text:
What is Nirvana (mahayana)?
...as per the title.
In the Theravada literature, the Buddha is seen as someone who found an end to suffering and taught that for all his life, urging his disciples to apply themselves to it, to not waste the opportunity and regret later.
While there are many interpretations of what exactly is Nirvana in this tradition (and what is/is-not a tathagata after death etc), it's perhaps universally accepted by it's adherents that embarking on this doctrine culminates in the permanent cessation of suffering. Some may speculate or say more about Nirvana, but others might be silent and not add anything that the texts don't say.
But what about Mahayana's Nirvana?

Is it the same same? Or is it more elaborated, like a realm where beings (Buddhas?) actually live?
Does it have the same requirements as the Theravada nirvana (e.g. elimination of the ten fetters, realization of four noble truths & dependent origination)?

Warning: To not make it too long, I avoided quotes. In addition, this is merely a summary. Just like with Theravada, there are interpretations. Since I present things in a traditional way, please do not take it personal when I seem to despise so-called Hinayana tenets or practices.

We say that a Hinayana arhat still has limitations, obstacles that prevent him from achieving the welfare of others as well as his own. On the other hand, a [fully enlightened] buddha abandoned all obstacles and thus is able to achieve the welfare of others, and achieved his own. This is because there are two obscurations that a buddha has abandoned:

Afflictive obscurations
Knowledge obscurations

Since a Hinayana arhat has uprooted ignorance - the root of samsara - he has abandoned afflictive obscurations. This is because ignorance, anger, desire, etc. are afflictive obscurations, and once the root has been abandoned, all the other afflictions  as well. However, a Hinayana arhat has not abandoned knowledge obscurations. Only a buddha has abandoned both obscurations.
There are four divisions of nirvana but I will speak of two. A Hinayana arhat achieved abiding nirvana. We also call it 'individual liberation' or 'solitary peace.' We say that this abiding nirvana is the extreme of peace. According to Asanga's Bodhisattvabhumi and other texts, after some time, the buddhas wake them up from their blissful individual liberation and tell them that more is to be done.
A buddha abides neither in the extreme of peace (abiding nirvana), nor the extreme of samsara. He achieved a non-abiding nirvana. He has abandoned the two obscurations and is, in this sense, beyond limitations. Therefore, he is able to benefit all sentient beings.
The way to abandon afflictive obscurations is by generating the wisdom of emptiness. Different Mahayna tenets posit emptiness differently, but they all posit the two selflessness: emptiness of person and emptiness of phenomena. As the Heart Sutra puts it:

Phenomena also are empty.

The way to abandon knowledge obscuration is by having the wisdom of emptiness conjoined with Bodhicitta. By generating spontaneous bodhicitta, one enters the Mahayana path of accumulation. On the Mahayana path of seeing, the wisdom of emptiness is conjoined with bodhicitta. When wisdom is imbued with bodhicitta, the mind becomes powerful and vast enough to abandon knowledge obscuration. We often refer to the following analogy:
The wisdom of emptiness is like an axe cutting through the two obscurations, while bodhicitta is a strong arm. Without bodhicitta, one's arm is not strong enough and can not abandon the two obscurations, thus achieving buddhahood. A Hinayana arhat has abandoned afflictive obscurations, but since he did not generate bodhicitta, he has not abandoned knowledge obscuration.
There are two divisions of knowledge obscurations:

The imprints of ignorance, and
The appearance of true existence that is caused by the imprints of ignorance.

Only a buddha is free from the appearance of true existence. Therefore, when a conventionality appears to a buddha, it does not appear together with the appearance of true existence and he realizes both truths simultaneously and with the very same mind: the omniscient mind of a buddha. On the other hand, whenever a conventionality appears to a sentient being (i.e. a non-buddha), it appears together with the appearance of true existence. Consequently, a sentient being cannot realize the two truths directly and simultaneously.
The omniscient mind of a buddha (the wisdom truth body dharmakaya):

Directly realizes the two truths, simultaneously
Is free from conceptualization, and unmistaken
Knows all existent, past, present and future

In addition, according to Mahayana, a buddha obtained the four bodies (kayas). There are ways of dividing the kayas into two, three, four, or five but we generally speak of four. A buddha has a mental body that is seen only by Mahayana aryas and that teaches them only the Mahayana Dharma. It is called Enjoyment body (Sambhogakāya). A buddha has body that is seen even by ordinary beings and this is the Emanation body (Nirmanakaya). We say that Shakyamuni Buddha was a supreme emanation body because he taught he possessed the 32 marks and the 80 signs. A buddha has an omniscient mind that we call "wisdom truth body". It gives birth to the teachings that emanate from it, like the rays of the sun emanate from the sun. It is by emanating in this way that he benefits all sentient beings (even though not all sentient beings interact with his teachings, but that is another subject of debate.)

Thank you for sharing this detailed answer and tradition.

What is the origin of Heart Sutra, and where are the original copies? Who drafted them and who is the author of Heart Sutra?

From a "religious" viewpoint, as His Holiness the Dalaï-Lama says, "The Mahayana teachings are rooted in the sermons that the Buddha taught
primarily at Vulture Peak." The Heart Sutra is one of them. It has 3 parts: (1) words that were permited by the buddha (2) words that were inspired by the buddha (3) the words of the Buddha's own mouth. There is much to say, even from a historical perspective. I suggest you create a question is you are interested.

Fom this answer I understand that nirvana/arahatship has the same requirements in both traditions. But parinirvana is not soteriological, or final, in Mahayana? In other words, for theravada it's not said much about parinirvana, usually no more than final freedom of suffering. But for Mahayana, after parinirvana, the Buddhas will wake that arahat and, once awaken, he will find that there's more to be done. So that blissful peace of his parinirvana is temporary? So final (really final) peace in Mahayana is when all beings attain nirvana? Is it correct to say that this Mahayana soteriology then?

Abiding nirvana is arhatship, but non-abiding nirvna is full enlightenment. Indeed, most Mahayana traditions posit that there is one final vehicle and that this final vehicle is the Mahayana vehicle. This "doctrine" of the one final vehicle is referred to as Ekayana. We believe that [Hinayana] arhatship is temporary, and that all arhats will have to enter the Mahayana path eventually to achieve buddhahood. Does it answer your question?

Certainly you did not say that you "despise" another branch of Buddhist practice other than your own? Isn't "despise" a word that describes hate? Regarding these "knowledge obscurations" that a Theravadin arahant has not relinquished . . . if such a person knows and directly sees that consciousness is not self (which is inherently a part of being an arahant) then how could such a person still cling to some type of knowledge?

You know, mya ngan las ‘das pa zhi ba’o means basically something like “Enlightenment is peace”. Sometimes it is considered like that. Peace. This of course misleads lots of people, thinking peaceful in the sense of – you know the standard peaceful like Koi Pond, Zen Garden, mountain, nobody bothering you. Weekend situation for instance. Or a holiday excursion to Hawaii, where you will not be bothered. Or also not only that, just even the religious sort of peace, like smiling, walking gently, brushing your teeth gently and with a mindfulness. All of that. That kind of peace, we talk about that kind of peace a lot.
Mya ngan las ‘das pa zhi ba’o, nirvana is peace. That peace has to go beyond that. In this case what is peace. Nonduality. Because the duality is the violence. The moment you create the duality it is a violence. It is a violence and it creates a lot of violence.
Let’s go back to our mirror situation. The moment you differentiate, the moment you divorce between the appearance of your face and the emptiness of your face in the mirror there is a violence. Why? Because when you divorce these two you are bound to fall into on of the extremes, either nihilism or eternalism. If you fall into that, then you will construct thesis. You will construct approach. And this is how it becomes violent. Nirvana on the other hand has deconstructed all the dualism, therefore actually the real peace, real ahimsa, I am say it is maybe under the second category. The peace, the nirvana peace is actually when you reach the nonduality, experience of the nonduality is the real peace.

Dzongsar Jamyang Khyentse Rinpoche

This topic is covered more than adequately in Wikipedia, see:
https://en.wikipedia.org/wiki/Nirvana_(Buddhism)
Of Early Buddhism it is said: "Most modern scholars such as Rupert Gethin, Richard Gombrich, Donald Lopez and Paul Williams hold that nirvāṇa (nibbana in Pali, also called nibbanadhatu, the property of nibbana), means the 'blowing out' or 'extinguishing' of greed, aversion, and delusion, and that this signifies the permanent cessation of samsara and rebirth.[34][35][36][37][38][quote 6]
According to Steven Collins, a synonym widely used for nirvana in early texts is "deathless" or "deathfree" (Pali: amata, sanskrit: amrta) and refers to a condition "where there is no death, because there is also no birth, no coming into existence, nothing made by conditioning, and therefore no time."[46] He also adds that "the most common thing said about nirvana in Buddhist texts is that it is the ending of suffering (dukkha)."[47] Gethin notes, "this is not a 'thing' but an event or experience" that frees one from rebirth in samsara. According to Collins, the term is also widely used as a verb, one therefore "nirvanizes."[46] Gombrich argues that the metaphor used in the texts of flames going out, refers to fires which were kept by priests of Brahmanism, and symbolize life in the world.[48] Nirvana is also called "unconditioned" (asankhata), meaning it is unlike all other conditioned phenomena.
The cycle of rebirth and suffering continues until a being attains nirvana. One requirement for ending this cycle is to extinguish the fires of attachment (raga), aversion (dvesha) and ignorance (moha or avidya). As Bhikkhu Bodhi states "For as long as one is entangled by craving, one remains bound in saṃsāra, the cycle of birth and death; but when all craving has been extirpated, one attains Nibbāna, deliverance from the cycle of birth and death."[49]"
As to the Mahayana conception of Nirvana it is stated:
"Nirvana is also described in Buddhist texts as identical to anatta (anatman, non-self, lack of any self).[95][96][97] Anatta means there is no abiding self or soul in any being or a permanent essence in any thing.[98][99] This interpretation asserts that all reality is of dependent origination and a worldly construction of each human mind, therefore ultimately a delusion or ignorance.[98][100] In Buddhist thought, this must be overcome, states Martin Southwold, through "the realization of anatta, which is nirvana".[100]
Nirvana in some Buddhist traditions is described as the realization of sunyata (emptiness or nothingness).[101] Madhyamika Buddhist texts call this as the middle point of all dualities (Middle Way), where all subject-object discrimination and polarities disappear, there is no conventional reality, and the only ultimate reality of emptiness is all that remains.[102]"
In otherwords, Theraveda emphasizes the extinguishing of afflictive obscurations, but the main thing to understand about the Mahayana view is the awakening to the realization of anatta, No Self, or Sunyata, Emptiness.


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Is Maha Brahma a GOD?
In Buddhism, we can find a name called "Maha Brahma".
Is he a GOD (as per Buddha, there are no such people called GOD), or some kind of different bean?

Mind blowing knowledge. Buddha will indeed be the greatest ever teacher the world has seen. No one else had courage to stand up against the ego of the gods. I cant understand why does the bible get so much attention in the world when there is nothing extra ordinary to it in comparison to the scriptures of the hindu, Buddhist and Jain faith.

Maha Brahma is a realm, and not “A GOD”. Any living being (including each of us) has been in all realms in this beginningless sansara. We have been at the highest (except the five pure abodes in rupa loka which can be accessed only by Anagamis or Non-Returners). One time the Buddha pointed to a bunch of ants on the ground and told bhikkhus that each of those ants had lived in a brahma loka. The sansara is that long; there is no discernible beginning. These 31 Planes of Existence  is described in the Dhammacakkappavattana Sutta. It lays out the “blueprint” of Buddha Dhamma.
In the realm of Great Brahmas (Maha brahma) Buddha mentions about one Great Brahma, a deity whose delusion leads him to regard himself as the all-powerful, all-seeing creator of the universe. It is in Kevatta (Kevaddha) Sutta: To Kevatta (DN 11). Kevaddha Sutta informs one of what even a “God” does not know. Maha Brahmas, like Baka, think they’ve gone beyond anything the Buddha knows, so the Buddha has to go up to their Brahma heavens and subdue their pride, to show
them that they still have more to let go of, that there is something the Buddha himself has gone beyond but they haven’t.
Dhammacakkappavattana Sutta lays out the “blueprint” of Buddha Dhamma, and in one part of it names the 6 deva realms and 15 out of 16 rupi Brahma  realms. The sutta is meant to convey the way to “see” the true nature of existence with wisdom, not with the physical eye. Only a Buddha can discover the true nature, but a human can comprehend it, once explained.
In the brahma realms, all brahmas are born fully formed without the help of a mother’s womb. Theirs is an “opapatika” birth. For example when a human dies, his body becomes inert like a log, and at the very instant a fully-formed brahma is formed in the appropriate brahma world. This brahma will have sense faculties appropriate for a brahma: only eyes, ears, and a mind. These are the indriya for the new existence. These indriya can become ayatana (a factory that produces sankharas of another birth)  at times depending on the activities of that brahma.
Male/female distinction is there only in the kama loka. In the brahma realms (higher 20 realms), there is no such distinction. Brahmas do not have dense physical bodies or sexual organs. One is born in either the 16 rupa loka realms or the 4 arupa loka realms (brahma realms) because one has given up all desires for bodily pleasures, including sex, because one has seen the value of niramisa sukha (and jhanic pleasures) that can be achieved by giving up bodily pleasures.
All brahma realms are “unisex“. Brahmas do not have dense bodies to experience touch, taste of foods, or smells. They have very fine bodies. A brahma “body” has only the most minute of matter that is much much smaller than an atom in modern science. This is why it is thought (erroneously) that there is no matter in arupa lokas. There is matter, but it is insignificantly small. The Buddha said that vinnana cannot exist without a pancakkhandha, and the pancakkhandha in the arupa loka has a rupa component, even though negligibly small.
Brahmas in rupa loka are removed from “coarse sense pleasures”; they do not have a desire for tastes, smells, or body touches. Seeing and hearing is enough for them. Brahmas in arupa loka do not even have a desire for sights and sounds. Mind pleasures are enough for them, and the presence of matter is minimal in the arupa loka. So, sense pleasures are absent in brahma loka.
Brahmas and devas can “see” humans engaging in activities (if they want to), but they do not have any liking (upadana) for such “coarse pleasures”. Their mental state is much higher, just like a human who has developed abhinna powers.  They could actually be repulsed by human bodies. Just like we do not “miss out” on the activities of worms, they are not interested in human activities. It all depends on the mindset associated with the particular bhava.
The brahmas (and also devas) can “see” without the aid of light and “hear” without the having air to transmit sound waves; their “physical bodies” do not have “eyes” and “ears” like ours. Thus they can “see” and “hear” over great distances. And they can be anywhere they wish within a short time. The closest analogy of how their “vision” works is how we “see” dreams; we don’t need eyes to see dreams. Likewise the brahmas just perceive.
See:  https://www.accesstoinsight.org/ptf/dhamma/sagga/loka.html

visudddhi excellent

On the question of Maha Brahma, it is clear from the Numerical Discourses of the Buddha i.e. the Anguttara Nikaya (AN 10.29 English translation by Bhikkhu Bodhi), in which the Buddha says " As far, Bhikkhus, as this thousandfold world system extends, Mahabrahma there stands as the foremost". Although the Buddha acknowledged the existence of gods, he focused on the Method to Liberate oneself from this endless cycle of birth and death. In this context, cosmology took a low priority in his agenda of teaching his methodology for liberation.

Maha Brahma is the being who exists when the universe first started expanding mistakenly thinking himself as an all-knowing, all-powerful, self-existent, eternal Creator. He seems to not know where He came from.
It seems that He is the same God spoken of in Abrahamic religions.

“Thereupon the being who re-arose there first thinks to himself: ‘I am
  Brahmā, the Great Brahmā, the Vanquisher, the Unvanquished, the
  Universal Seer, the Wielder of Power, the Lord, the Maker and Creator,
  the Supreme Being, the Ordainer, the Almighty, the Father of all that
  are and are to be. And these beings have been created by me. What is
  the reason? Because first I made the wish: “Oh, that other beings
  might come to this place!” And after I made this resolution, now these
  beings have come.’" (DN 1)

Through the intense practice of metta (loving-kindness) one can attain the Brahma realm (Heavenly World of the Creator).
That heavenly world lasts for such an extremely long time period it's mistaken as eternal by other teachers but eventually it disappears and comes to an end so it's not a solution to ending suffering.
Deities in the Pure Abodes, arahants, paccekabuddhas, and sammasambuddhas are superior in terms of power and knowledge to Maha Brahma.
In Iti 22 the Sammasambuddha Gautama recalls that in a past existence He himself was Maha Brahma as a result of intensely practicing metta.
Maha Brahma is only one, appears in the beginning of the universe, and has an amazing appearance.
Maha Brahma like other deities are better defined as "higher beings" rather than as gods.
He is a God-like figure but not actually all-powerful or all-knowing.

There are beings who are born as Maha Brahamas in the highest realms of existence. Since their life span is extremely long and they see people are born and die, having forgotten their own prior birth (due to their long life) some of them fall into the illusion they are like the rulers, creators or supreme of the world. On a certain occasion, Buddha has spoken to such beings having noticed their thoughts.

Indeed there is Brahma. What you see, hear, touch, felt and see is actually experienced by Brahma. He is the seer behind all individual and the root of samsara. Samsara where one takes birth, grow old and dies is samsara, means the body of Brahma. But delusionally individuals in it think that they are different, do deeds as good and bad and gets the result of rebirth. But actually this whole world of men, animals, birds, maggots, reptiles are his forms, means he is the silent witness who enjoy the action they do. So, whoever talks of universe is Brahma is talking truth but when they say it's eternal is wrong. Because it changes very rapidly. Brahma, who is non-eternal, changing take the fool as eternal and non-changing.
So, Brahma world is samsara of sin and virtue.
Only realised one found the escape. How?
Throw away that, which is not yours! Why? Because it belongs to Brahma. Body, senses, mind, feeling, counsiousness is not yours....are changing......are suffering....are the branches of pain....And the root is Brahma.
So, there is path of purity to attain nirvana. Nirvana means total extinction of samsara and it's root, brahma.
The path appears sudden like a shock in invidiual who detached and rightous. That light is Inner master, Hari, what buddha called as "Anatta". It's eightfold path. Why not seventh? Well, the 7th is Brahma, the root of pain. Veda stumbled onto the 7th Brahma and sang his vain glory. It's like one worship the enemy.
Anitya is synonym for Brahma and Anatta is synonym for Inner master. So, conclusively self is utter illusion from individuals point of view.
Because, there is two truth, one is root of suffering(Brahma) and other is way of relieving the suffering (Inner master, Guru, Hari, Anatta, highly Lord greater that brahma).
Whoever found the true meaning of Anatta, receive food while begging. Why?
Imagine the whole world is Brahma which is root of pain in samsara. So, whoever got awaken will use his tools? Can he pluck out the fruit from tree of Brahma and eat it while knowing it is mixed with poison?
So, awakened one doesn't regard to this body and eat only extent to that which sustain their life by begging without humiliation. Why don't they disappear although know this whole world is root of pain? Because of only compassion to the living ones and he know how to deliver them. So, they live for the sake of others, do actions for the sake of others but never ever they go astray. They are like lotus amid pond and clay. Lotus is Anattta and dirty soil is Brahma.
So, there is no great brahma because Brahma is not great. In fact he should devout to Inner master and clean his Sin.
May all find peace!

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Are there Bodhisatta practices within Theravada?
In the Majjhima Nikaya, there are mentions of Bodhisattvas.
For instance, Bhayabherava Sutta (4. Fear and Dread) says:

"Before my enlightenment, while I was still ony an unenlightened Bodhisatta..."

It is a sentence that is repeated throughout the MN.
The Acchariya-abbhuta Sutta (123. Wonderful and Marvellous) also says:

"Mindfull and fully aware, Ananda, the Bodhisatta appeared in the Tusita heaven."

I have two questions:

Are there Bodhisattva practices in Theravada? (such as the cultivation of Bodhicitta and the six perfections presented in Mahayana traditions)
Since we find occurrences in the Pali Canon, why do we often hear that the notion of bodhisattva is a late notion?

This is a good question. So far wading through the Tipitaka i haven't seen any references to practices of a bodhisatva and no encouragement to follow such practices.

The way of a bodhisattva with proper motivation meets all requirements for arahantship and buddhahood except time, correct?

Bodhisatta practices in Theravada are mentioned in Buddhavamsa, Jataka and Apadana atthakatha, especially in Visuddhajanavilāsiniyā, Apadana Atthakatha, the commentary of Apadana, which is believed to be a late addition to the Pali Canon, added after the Second and Third Buddhist Councils. This is probably why we hear that the notion of bodhisatta is a late addition. However, in Theravada countries like Sri Lanka where I come from, the bodhisattas are widely accepted. (See also the wikipedia section on Theravada bodhisattas. https://en.wikipedia.org/wiki/Bodhisattva)
According to Buddhavagga section in Apadana Atthakathaa, Theravada Buddhism has ten perfections dasapāramitā (Giving, morality, renunciation, wisdom, energy, patience, truthfulness, determination, loving kindness and equanimity)
and there are three types of bodhisattas, the ones aspiring to be Sammāsambuddha, Pacceka Buddha (a private Buddha) and Savaka Buddha (arahant).
According to the section Buddhavagga in Apadana Atthakathaa, to become a Sammāsambuddha, one requires either 4x10^140 (cattāri asaṅkhyeyyāni), 8x10^140 (aṭṭha asaṅkhyeyyāni) or 16x10^140 (soḷasa asaṅkhyeyyāni) eons of pāramitā perfection

‘‘buddhānaṃ, bhante, patthanā kīva ciraṃ vaṭṭatī’’ti. Buddhānaṃ,
  ānanda, heṭṭhimaparicchedena cattāri asaṅkhyeyyāni
  kappasatasahassañca, majjhimaparicchedena aṭṭha asaṅkhyeyyāni
  kappasatasahassañca, uparimaparicchedena soḷasa asaṅkhyeyyāni
  kappasatasahassañca
  Apadana Atthakathaa

depending on whether he has high wisdom (Paññādhika), faith (Saddhādhika) or effort (Vīriyādhika).

Ete ca bhedā paññādhikasaddhādhikavīriyādhikānaṃ vasena ñātabbā.
  Paññādhikānañhi saddhā mandā hoti, paññā tikkhā. Saddhādhikānaṃ paññā
  majjhimā hoti, saddhā tikkhā. Vīriyādhikānaṃ saddhā paññā mandā hoti,
  vīriyaṃ tikkhanti.
Apadana Atthakathaa

A bodhisatta aspiring to be a pacceka buddha requires 2x10^140 (dve asaṅkhyeyyāni) eons of practice.

paccekabuddho paccekabodhisattabhūmiṃ ogāhanto dve asaṅkhyeyyāni
  kappasatasahassañca pāramiyo pūretvā
Apadana Atthakathaa

For an arahant a time limit is not given for the bodhisatta period.

Downvoters better provide a reason as I've given a proper Theravada source in my answer.

Thx for answer. You say Pacceka Buddha  are a type of bodhisattvas. Does it not contradict Saptha Visuddhi's assertion that "The Bodhisatta ideal is the sphere or domain (vishaya) of the seven Buddha" ? I say that also because according to Mahayana, a Pratyekabuddha is on a Hinayana path and is thus not a bodhisattva.

@TenzinDorje I think he's referring only to the suttas compiled at the 1st council. In those, we only encounter the 7 Buddhas as bodhisatta. As I've mentioned in my answer, Apadana atthakatha was inserted only after the 2nd council. In apadana atthakatha one aspiring to be a paccekha buddha is clearly mentioned as a paccekhabodhisatta. See my edited answer.

Just out of curiosity, do any Theravadin practice the bodhisattva ideal (the 10 perfections, if I understand), based on the Canon set after the 2nd council?

@TenzinDorje In short, yes. I personally know a Buddhist monk who's aspiring to be a Buddha and there were a few monks (public figures) in Sri Lanka who claimed they were Bodhisattas.

Where they really holding Hinayana tenets, thinking that he Mahayana sutras are not the words of the buddha?

@TenzinDorje If you mean Hinayana to be Theravada then yes. The monks I mentioned do not refer to Mahayana suttas. As an example Ven. Ananda Maithreya thero aspires to be a Buddha  https://en.wikipedia.org/wiki/Balangoda_Ananda_Maitreya_Thero

Every reference that is ever made to a “Bodhisatta” in the Theravada Suttas is in relation to the Present Supreme Buddha, or the six other Buddhas that appeared in the last 91 aeons. Thus the Bodhisatta ideal is the sphere or domain (vishaya) of the seven Buddha that has appeared  and the One yet  to come.
Edward Conze was a Mahayana scholar, translated the Mahayana Prajnaparamita or Perfection of Wisdom sutras from original Sanskrit to English.  In the words of Edward Conze:

” “……About 100 BCE (roughly 400 years after the Buddha’s  Parinibbana) a number of Buddhists in India felt that the existing statements of the doctrine had become stale and useless. In the conviction that Dhamma required ever new re-formulations so as to meet the needs of new ages, new populations and new social circumstances, they set out to produce new literature which ultimately came to known as Mahayana Buddhism. The creation of this literature is one of the most significant outbursts of creative energy known to human history and it was sustained for about four to five centuries. Repetition alone, they believed, cannot sustain a living religion. Unless counterbalanced by constant innovation, it will become fossilized and lose its life-giving qualities, they believed”.

There are five doctrinal “innovations” of the Mahayanists that have been listed by Edward Conze. They are:

•  As concerns the goal there is a shift from the Arahant-ideal to the Bodhisattva-ideal;
  •   A new way of salvation is worked out, in which compassion ranks equal with wisdom, and which is marked by the gradual advance through six “perfections” (paramita);
  •   Faith is given a new range by being provided with a new pantheon of deities, or rather of persons more than divine;
  •   “Skill in means” (upayakausalya), an entirely new virtue, becomes essential to the saint, and is placed even above wisdom, the highest virtue so far;
  •   A coherent ontological doctrine is worked out, dealing with such items as “Emptiness”, “Suchness”, etc”.

The oath in most Mahayana traditions to, “not to seek Enlightenment until ALL BEINGS ARE READY for Enlightenment” is the most visible contradiction to that of Theravada. The first thing one is supposed to do in becoming a “Mahayana Buddhist” is to take the “Bodhisattva vow”:They say each being should endeavor to become a Buddha i.e., each person should become a Bodhisattva. The historical timeline of the rise of Mahayana is discussed in detail by Edward Conze in his book,  “A Short History of Buddhism” (1980). According to Conze, the history of Buddhism can be conveniently divided into four periods:

•  The old Buddhism, which largely coincided with what later came to be known as Theravada
  •   Rise of Mahayana,
  •   Rise of the Tantra (Vajryana) and Ch’an (Zen),
  •   No further divisions.

Since we find occurrences in the Pali Canon, why do we often hear that the notion of bodhisattva is a late notion?

It seems to me, practices for bodhisattva are mostly (or fully?) absent, and don't find nearly as much encouragement in the Nikayas/Agamas from the Buddha (or no encouragement at all? I don't recall reading any sutta where he would inspire anyone to do it). So, even though these texts refer to bodhisattvas, I guess there isn't really an actual practical path there or fully developed motivation for it, to become an ideal. But the idea that this is something one can do is there and I've read about ancient non-mahayanists taking that goal for themselves.
One related study on this is Bhikkhu Analayo's The Genesis of the Bodhisattva Ideal.

From general knowledge I gleaned the conventional Theravada appeared in the English world doesn't practice for Bodhisattva. They admit 7 Buddhas included the future Maitreya as the totality of all in eons of Kalpas plus endless spacetime/universes. The highest goal of conventional Theravada is not a Buddha - there is no chance/ only 7 Buddhas existed the last one has already been claimed by Maitreya - but Arahat, who ended sufferings by realized Nibbana.
Why the conventional Theravada said the Bodhisattva is a late notion, because the scholars said so. Like Saptha Visuddhi quoted Edward Conze in her/his whole post, Edward Conze's scholastic studies are equally as true as the Suttas, if not more scientifically correct with archaeological evidences!
I didn't read Edward Conze, so I have no comment on Edward Conze's scholastic study however he laid hands on Mahayana didn't endorse him the authentic knowledge on the Mahayana teaching hence enabled him to conclude his conclusions. But by Saptha Visuddhi's interpretation of “Bodhisattva vow” if s/he derived her/his understanding from Edward Conze then it is wrong. Bodhisattva is already enlightened, but not entering Nirvana until all the beings are ferrying to the "other shore"/ free of suffering. It will take too long paragraph to explain for the English sect has too many wrong terms and wrong understandings.
In 《解深密經》 the Buddha explaint when some Bodhisattvas seeing the horror of Naraka and other lower realms they were too horrified and could't endure Samsara anymore, they can choose to enter Nirvana, (I think these refer to the Hinayana sect's practice, need re-check the Sutra). But the higher level (esp. 8th level and above) will continuous to overcome those until reached perfect wisdom - Anuttara-samyak-sambodhi 等正覺, Buddha.

According to mahayana a bodhisattva with proper motivation is equivalent to a theravedan arahant.
So bodhisattva practices that are also theravedan are solely the practices of an arahant!

"vadins always so funny " - please let this place (buddhism.stackexchange) a peaceful place for real question, answer and discussion. I'm flagging this to the moderation.

Yes I deleted that first sentence (see the edit history). If you look at the FAQ index (summary of site policies) you'll see that a lot of the topics there are categorised as "Minimizing controversy" (between different views and sects). That was a concern of the community when they established this site -- people of one school disparaging another (or even "making fun of it") isn't done here. Doing that is too easily misinterpreted, so please don't do it at all.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


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Where in the Vimalakīrti Sutra is this stated?
I was reading some of the writings of Nichiren Daishōnin, and I came across this part where he says that it states in the Vimalakīrti Sutra that, "if the minds of living beings are impure, their land is also impure, but if their minds are pure, so is their land. There are not two lands, pure or impure in themselves. The difference lies solely in the good or evil of our minds" (On Attaining Buddhahood in this Lifetime 4).
I assume that he was paraphrasing, but I couldn't find any footnotes about were he got this from. I've never read the Vimalakīrti Sutra, but if there is a passage where this message could have been taken from, I'd be happy to see it.
Thank you!

In this translation, the text quoted below exists about 10% of the way through the text, towards the end of the first chapter ("1. Purification of the Buddha-Field"), a few paragraphs before the start of the secod chapter ("2. Inconceivable Skill in Liberative Technique"):

Thereupon, magically influenced by the Buddha, the venerable Sariputra had this thought: "If the buddha-field is pure only to the extent that the mind of the bodhisattva is pure, then, when Sakyamuni Buddha was engaged in the career of the bodhisattva, his mind must have been impure. Otherwise, how could this buddha-field appear to be so impure?"
The Buddha, knowing telepathically the thought of venerable Sariputra, said to him, "What do you think, Sariputra? Is it because the sun and moon are impure that those blind from birth do not see them?"
Sariputra replied, "No, Lord. It is not so. The fault lies with those blind from birth, and not with the sun and moon."
The Buddha declared, "In the same way, Sariputra, the fact that some living beings do not behold the splendid display of virtues of the buddha-field of the Tathagata is due to their own ignorance. It is not the fault of the Tathagata. Sariputra, the buddha-field of the Tathagata is pure, but you do not see it."
Then the Brahma Sikhin said to the venerable Sariputra, "Reverend Sariputra, do not say that the buddha-field of the Tathagata is impure. Reverend Sariputra, the buddha-field of the Tathagata is pure. I see the splendid expanse of the buddha-field of the Lord Sakyamuni as equal to the splendor of, for example, the abodes of the highest deities."
Then the venerable Sariputra said to the Brahma Sikhin, "As for me, O Brahma, I see this great earth, with its highs and lows, its thorns, its precipices, its peaks, and its abysses, as if it were entirely filled with ordure."
Brahma Sikhin replied, "The fact that you see such a buddha-field as this as if it were so impure, reverend Sariputra, is a sure sign that there are highs and lows in your mind and that your positive thought in regard to the buddha-gnosis is not pure either. Reverend Sariputra, those whose minds are impartial toward all living beings and whose positive thoughts toward the buddha-gnosis are pure see this buddha-field as perfectly pure."

I hope you'll get a better sense of it if you read that whole first chapter.


text:
Recognition of Ignorance on a Topic
I have read many Q&As here on ignorance but I am concerned with the recognition of my own ignorance on particular topics. I feel like recognizing my ignorance helps me to reduce my identification with my limited understanding and the opinions and emotions this brings up. I feel like it keeps me from feeling any need to argue about things I recognize I am not well informed about, and rather communicate how my limited understanding connects to things I believe in. For lack of a better word it seems to help me with equanimity, this posture of recognizing that I just don't know.
Maybe ignorance is the wrong word, but I am wondering if Buddhism addresses this idea.

I think that in this topic you're not asking for a simple definition of Avidyā. Instead I think you're saying that you find it better to "recognize ignorance" when it exists (instead of perhaps identifying with, grasping, or arguing in favour of a wrong view); and you're asking whether Buddhism addresses (has more to say about) this seemingly-beneficial aspect of recognition-of-ignorance.

Precisely. You have expressed my real question well.

These suttas might be relevant to what you're asking about:

Paramatthaka Sutta (SN 4.5)
Kaccaayanagotto Sutta (SN 12.15)

I think that what the OP is describing is not "ignorance" -- it's describing not getting attached to views, not getting into arguments about views.
The second statement in the OP, i.e. "communicate how my limited understanding connects to things I believe in", might be related to dharma being something you should "see (or know) for yourself".
Also (in a different way from the suttas above) I think that this answer is a description of living with ... let's call it "uncertainty" rather than "ignorance".

I like the use of the term uncertainty here. If ignorance is a lack of knowledge but there is no such thing as complete knowledge, then uncertainty captures the idea of "I know not enough to be certain" without assuming there is some perfect state of "knowing all" so as to be free of ignorance on the matter. Uncertainty captures the practice in my mind of being able to say to others that I am not knowledgeable enough to assert my opinion with much certainty.

Paramatthaka Sutta appeals the most to me as an answer. Thank you.
I like to say "The world is too complex for me to know it is right to rain tomorrow." This captures that essence. I can learn all there is to learn yet still realize my opinion on the rightness of rain is only a formulation of my ego. I feel like we live in a world where people think "the one with the most facts wins" But to me this feels like attachment. Uncertainty says to me "I do not know but this is how I feel" and it allows me to feel differently tomorrow and it leaves open room for how everyone one else feels.

I heard a talk recently in which a Zen master said ignorance in Buddhism really meant a lack of awareness of the mind (i.e. letting it wander in stories and daydreams), rather than the normal meaning of ignorance.
I don't know if this is orthodox Buddhism (or orthodox Zen for that matter), but it makes more sense to me than interpreting 'ignorance' as factual ignorance.

Ignorance is a bad word, a bad translation. Avija means "state of not knowing". Just like you said. We are all identifying unless we are enlightened or something. Do you mean that you are aware of what you don't know? Like seeing things as they are + the '"not knowing"? .. with practice, the "not knowing" will slowly leave. I hope I understood you correctly- Metta

Yes. Ignorance sounds bad and when I look it up in relation to Buddhism I seem to find this Avija which seems to be more about a lack of awareness of the mind or the nature of reality. But here I just mean that I feel like there is something within Buddhism that speaks to the recognition of one's limited understanding of a particular matter.

@Greg Well, we don't really 'need' to know. We need to be wholesome, be mindful and recognize our limitations. Then knowing just happens. There is no striving for vija(knowing). Oh yes, we need to be aware of our limitations in avija, intellectual knowledge ,endurance and courage. We should be gentle with ourselves and at other times be strict with ourselves. Just like a teacher would.  The more we practice the better our inner teacher can teach us, so to speak.-Metta

Avijjā / Moha in refers to not knowing the Three marks of existence at the experiential. It is not necessarily being ignorant about the subject matter may it being even a Buddhist theory.
Also one way the Buddhist practice can be viewed as is: pariyatti (theory), patipatti (practice), pativedha (experience / verification). Hence it is vital to learn the theories and it is this which will be validated and verified through the practice. More you need knowledge gaps try your best to learn and fill them.
Also do not let you mind get disturbed due to any knowledge gaps. Be equanimous, than being jubilant, develop ego, when you know more and let down when you know less.

You are concerned about the cup of water you are holding (ignorance on a particular topic, and your reaction to seeing your ignorance of that) when you are standing in the ocean up to your neck (ignorance - the basic condition for existence until enlightened).
The Upanisa Sutta lists the Supporting Conditions for enlightenment, and at the very bottom - the fundamental condition - is Ignorance. This word comes from the word Gnosis: to know. So ignorance simply means, to not know. There is nothing shameful or embarrassing about that, we are all born that way. So, it is not bad or blameworthy, it just means: get some knowledge.
You can never know everything, so there will ever be "ignorance on a particular topic", but you are not called to know everything, you must only know how to run your own life: how to have equanimity and balance, and to respond skillfully. (That wasn't so dreadful, now was it?)
Enlightenment is not so incredibly high a bar; stop thinking it is far off. Like awakeness when you are asleep. You will get there inevitably. Then the ocean will be drained and you can walk across.

I appreciate the response, it is eloquent. But it doesn't seem to match my question. I'm not worried or ashamed. I said I thought my recognition of my ignorance was helpful and wondered if Buddhism had something to say about this. I did not ask about enlightenment or say I thought it was difficult or far away.
I also don't see how you can reconcile "get some knowledge" with both the assertion that ignorance is a fundamental condition for enlightenment as well as the assertion that there one will always be ignorant. If knowledge is a bottomless well, why would you ask that I jump down it?

I apologize for an unclear response, thank you for asking. Yes, you are not concerned, I suppose I was trying to write a more general answer and missed the mark. My main point was to mention the Upanisa Sutta, which I have found extraordinarily helpful. It lists a series of stages, and I have seen some of these in my progress. The message of the sutta is positive, and I think that the idea of 'ignorance' is often misunderstood. Perhaps I was trying too hard. But this sutta seems to directly fit with what you asked about.


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Feeling concern for others but like my efforts in anything are wasted
I feel concern for others, but like my efforts in anything are wasted. Is there any practice I could engage in, to remedy the latter?
I've been taught meditation in a handful of contexts. What about sort of focusing on or keeping that feeling of nothing mattering, during zazen?
Caveat: I won't believe in other lives, only karma.

I feel concern for others, but like my efforts in anything are wasted. Is there any practice I could engage in, to remedy the latter?

Act of the betterment of other, but do not be attached to the outcome, as you have to practice equanimity, also as part of the Brahmavihara. Otherwise the practice will become a burden and a stress, than away to unburden yourself. I.e., be concerned but not stressed, when the outcome is not what is intended.

Caveat: I won't believe in other lives, only karma.

Attachment to beliefs is also attachment which can give arise to stress. Generally it is best to avoid believes in the line "this exits or does not exists, that exists does not exits". But having said this you need a set of Right Beliefs but even to these do not get attached.


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If each person's mind creates "reality" then why do we need to eat?
My teacher has been talking about how each person's reality (including the body) is in fact an illusion generated by the mind in each moment. As an extension of this, she teaches that there are no "good" or "bad" people, things or circumstances - the way things appear and the qualities they have are all coming from my own mind.
I think I kind of understand this as a metaphor, but I don't understand how she can seem to literally believe this: for example, during the teaching session I was very hungry. I thought, "I can meditate and come to ignore how hungry I am- but if I did that every time, one day I would die of starvation, whether I was aware of that in my mind or not. So surely hunger is actually "real" and not just in my mind - because it will lead to me dying unnecessarily unless I react to it?"
Another example I thought of was murder. I can believe everyone is neither good nor bad, and via compassion, everyone will seem good. But surely it doesn't matter how I imagine a situation is going in my mind - if I meet someone who tries to murder me, for example, they will kill me, regardless of how loving I believe them to be. My death would occur regardless of my mind (but if I had listened to my mind, I might have been able to avoid the death that would result from interacting with that person).
I understand that death isn't "good" or "bad" either - but how does the dharma explain the division between "mind reality" and actual physical reality that can kill me no matter what my mind does? Another quick example: medication for mental illness. I had a teacher once who endorsed mentally ill people stopping all medication, because it was only a placebo - but if that's true then why is it that an unmedicated schizophrenic (for example) would be physically unable to meditate (and cure themselves, as my teacher suggested) most of the time, as they would be too ill to concentrate? Isnt that an example of physical chemicals (drugs) being "stronger" than the mind (calming the mind so that it can begin to meditate)?
Apologies if I'm being ignorant, or if I sound critical. I feel like I'm missing some vocabulary that would help me explain better. Thanks for reading :)
(Edit: I also have a very similar question/example: why does it result in good karma when you feed starving people, if the food, the pain of starvation, and even your good deed is just an illusion in the minds of you and the starving person? Obviously if I had a sandwich, and I saw a child who was hungry, I'd give them all of the sandwich. But then isnt the child receiving negative karma for causing ME to go hungry, even though it was my choice? And why bother at all if only karma is real - the child's hunger isn't "real", so why end it?)

What buddhist sect does your teacher teach ?

Both teachers I mentioned are part of the New Kadampa organisation, as this is the only one I have access to. I don't know if the part about medication is part of their beliefs (as to me it seemed like it could be harmful message & not one that I've heard associated with Buddhism before.)

Google suggests there are controversies associated with NKT. This page claims that "no medication" is or was part of what some of their teachers teach/taught.

Being New Kadampa, should this be tagged as mahayana and/or tibetan buddhism?

@ThiagoSilva It may be too late to do that: the tag would invalidate existing answers, which were posted before that tag was added to the question. When the OP posted their question and people answered, it was not apparent that the OP was asking for an answer specific to any particular tradition.

an illusion generated by the mind in each moment
Hunger is a complex phenomenon:

"Name" and "form" (an absence of so-called food in the so-called stomach, with associated changes to the metabolism and sensory nerves)
Consciousness of the sensations (probably a series of moments of consciousness, not a continuous consciousness)
Feeling (how you feel about or perceive that sensation, for example, "this feels unpleasant")
Craving ("I want the feeling and sensation to be gone, I want my craving to be satisfied")
Attachment (deciding that "Food is the stuff which would satisfy this craving: I want food!")

Most of this is "mental", including your naming the components (hunger, stomach, food, etc.).
An analogy might be, watching a movie: the movie might be 'based on a true story' and even have 'real' actors, but by the time it's been turned into a movie there's a large illusory or mind-made component.
I think it isn't only an illusion though. Before he became enlightened the Buddha tried not eating: it's said he found that interfered with meditation, and he therefore chose the doctrine of the "middle way" (neither the extreme of asceticism nor the extreme of hedonism).
Buddhism has a lot to say to people about food (e.g. right behaviours and right attitudes to have, about food), and especially to monks.
why do we need to eat?
One theory is that human life is a good opportunity to experience dharma e.g. that things aren't permanent nor permanently satisfactory. Allegedly there are other, formless being in higher planes of existence, who don't need to "eat" as such, on the other hand it's hard or impossible for them to learn dharma.
So surely hunger is actually "real" and not just in my mind - because it will lead to me dying unnecessarily unless I react to it?
Consider the opposite side of that story too, though: people over-eat because they think they're hungry. Or they crave for the repetition of any number of other experiences.
The word "real" comes from the Latin word for "thing". I think that hunger has a real component, but also many mental components.
"My death" (i.e. "me" and "dying") are both concepts, too.
it doesn't matter how I imagine a situation is going in my mind
On the other hand it does matter: because most people aren't trying to kill you; if you go around thinking "this person may want to kill me" that has consequences (for example in how you behave, how you see yourself, and how people react).
why is it that an unmedicated schizophrenic would be physically unable to meditate
My experience is that an unmedicated schizophrenic may well be able to meditate; but they may have trouble communicating with other people, and/or other people have trouble communicating with them; and various social activities (wanting and keeping a job for example) may be difficult.
It depends on the person, and the situation, who's with them and how they react; depends on the medication too.
It's complicated, and psychiatric medications are simplistic, sometimes effective, sometimes not, often with undesirable physical side-effects but sometimes (depending) better than nothing.
So I don't agree with the teacher if they said "mentally ill people stopping all medication, because it was only a placebo" -- some medications aren't "only a placebo" and some patients benefit from them.
I also don't agree with your statement: it may be true that some people can't or don't meditate, it just isn't always true, in my experience.
I feel like I'm missing some vocabulary that would help me explain better
Two useful bits of vocabulary are "middle way" and "two truths".
"Middle way" has a specific historical meaning,

There are these two extremes that are not to be indulged in by one who has gone forth. Which two? That which is devoted to sensual pleasure with reference to sensual objects: base, vulgar, common, ignoble, unprofitable; and that which is devoted to self-affliction: painful, ignoble, unprofitable. Avoiding both of these extremes, the middle way realized by the Tathagata — producing vision, producing knowledge — leads to calm, to direct knowledge, to self-awakening, to Unbinding.

That historic meaning is especially relevant to food. I think "middle way" might also be used more generally, to mean avoiding other extremes: for example, "the world is just an illusion" is one extreme, and "thoughts are real" is maybe another extreme, and we're supposed to learn to avoid both these extremes, and to see each view in a proper context. There's a kind of nihilism that's explicitly defines as a "wrong view":

And what is wrong view?

'There is nothing given, nothing offered, nothing sacrificed. There is no fruit or result of good or bad actions. There is no this world, no next world, no mother, no father, no spontaneously reborn beings; no contemplatives or brahmans who, faring rightly & practicing rightly, proclaim this world & the next after having directly known & realized it for themselves.'

This is wrong view.

There's a lot written about "two truths" and I think that different schools of Buddhism may have said different things about it. I think that an example of "two truths" might be that, "I exist and I am Chris" is a so-called conventional truth, whereas "there is no thing which can be called Chris, Chris is a name applied to an assemblage of parts" is a so-called ultimate truth ... and they are both true, they are both truths (but perhaps also both untruths if they're merely concepts).
Then there's a non-duality doctrine (perhaps from later schools of Buddhism) which says that these two truths (conventional and ultimate) are one.
Another concept that may be worth remembering is that of "attachment to a view". A "view" is something fairly fixed or permanent (see e.g. the answers to this question). And having a fixed view, being attached to a specific view, may be unwise. Again it's a balancing act, i.e. Buddhism does define a set of views as "right" (i.e. "right view"), but also warns e.g. here or here or even here not to grasp at, not to argue about, not to be imprisoned by dogma.
why does it result in good karma when you feed starving people
A couple of reasons, one is that compassion and so on are meant to be the right way to behave socially:

These four attitudes are said to be excellent or sublime because they are the right or ideal way of conduct towards living beings (sattesu samma patipatti). They provide, in fact, the answer to all situations arising from social contact. They are the great removers of tension, the great peace-makers in social conflict, and the great healers of wounds suffered in the struggle of existence. They level social barriers, build harmonious communities, awaken slumbering magnanimity long forgotten, revive joy and hope long abandoned, and promote human brotherhood against the forces of egotism.
The Brahma-viharas are incompatible with a hating state of mind, and in that they are akin to Brahma, the divine but transient ruler of the higher heavens in the traditional Buddhist picture of the universe.

Another reason is, I think, that we may tend to be selfish, to have thoughts like, "this is my hunger, this is my food, I am more important than they are" ... and that kind of egoism is a cause of suffering. See also Dana.
Within a lay context (i.e. if you're not a monk who has nothing) perhaps you're supposed to find some balance (i.e. non-extreme) in your giving too.
But then isnt the child receiving negative karma for causing ME to go hungry, even though it was my choice?
No: the giving is your choice, your intention, your karma.
And why bother at all if only karma is real - the child's hunger isn't "real", so why end it?)
I like this Zen story:

Nothing Exists

Yamaoka Tesshu, as a young student of Zen, visited one master after another. He called upon Dokuon of Shokoku.
Desiring to show his attainment, he said: "The mind, Buddha, and sentient beings, after all, do not exist. The true nature of phenomena is emptiness. There is no realization, no delusion, no sage, no mediocrity. There is no giving and nothing to be received."
Dokuon, who was smoking quietly, said nothing. Suddenly he whacked Yamaoka with his bamboo pipe. This made the youth quite angry.
"If nothing exists," inquired Dokuon, "where did this anger come from?"

I think the point of the doctrines of emptiness and non-self is to avoid unwise attachment (e.g. "this is me! this is mine!"), which would cause suffering (e.g. "this is changing, this is being lost, so woe is me!").
And anger (and probably hurt pride) and so on is a prime example of an afflictive emotion (see e.g. "unwholesome factors" listed on this page; or "poisons" listed on this page).
There are other examples of Zen stories which I think are intended to inform us how we ought to be behave -- this one, for example, is relevant to feeding a hungry child:

Is That So?

The Zen master Hakuin was praised by his neighbours as one living a
pure life.
A beautiful Japanese girl whose parents owned a food store lived near
him. Suddenly, without any warning, her parents discovered she was
with child.
This made her parents angry. She would not confess who the man was,
but after much harassment at last named Hakuin.
In great anger the parent went to the master. "Is that so?" was all he
would say.
After the child was born it was brought to Hakuin. By this time he had
lost his reputation, which did not trouble him, but he took very good
care of the child. He obtained milk from his neighbours and everything
else he needed.
A year later the girl-mother could stand it no longer. She told her
parents the truth - the real father of the child was a young man who
worked in the fishmarket.
The mother and father of the girl at once went to Hakuin to ask
forgiveness, to apologize at length, and to get the child back.
Hakuin was willing. In yielding the child, all he said was: "Is that
so?"

Reminds me of Byron Katie's question, "Is it true?"

"Illusion" and "reality" mean specific things in Buddhism. "Illusion" means attaching to the mental baggage we add to our experience -- the cause of our suffering.  "Reality" is our experience devoid of this attachment. If you keep this in mind, you won't go astray. So either you misunderstood your teacher and her message was more subtle, or your teacher has missed the point and you should ignore her.
So if you don't eat food, you will starve.  The illusion here is when you cling to the mental baggage that accompanies this experience.  For instance, with the hunger, you start to think things like the following...

I shouldn't be hungry
I wish I was eating X
Why did I skip lunch?

Now as long as you are mindful of these thoughts as simply thoughts arising, you're ok.  But when you cling to them, then you are under the spell of the illusion, and you suffer
Likewise, if you help those in need, you will make their lives better. The illusion happens when you cling to the mental baggage that arises in this situation.  For instance, you see people in need.  Fine.  But now you might start adding to this feeling thoughts like the following...

Why must we live in a world where this happens?
Why won't anyone help them?
X is responsible for this!

Again, to the extent that you recognize these as simply thoughts arising, you are ok.  But when you cling to them, you are under the spell of illusion and you suffer.
Even an apparently positive thought can be a problem.  For instance, when you help someone, you might experience this thought arising...

I am a great person for helping

You may cling to it, and it may make you feel good.  But it can sow the seeds of suffering because now you might get attached to this image of yourself as a good person and when it's challenged down the road, you can suffer.
Again, the issue here isn't thought, it's attachment to thought.  Some thoughts are good guidelines for actions, while others simply cause you to suffer.  Some do a bit of both.  But in all cases, don't attach to them -- recognize them as thoughts and choose what to do about them -- if anything.

"My teacher has been talking about how each person's reality (including the body) is in fact an illusion generated by the mind in each moment."
I don't know much about New Kadampa, but other Buddhist traditions don't really mean that reality is a creation of the mind. But rather that, because of a lack of understanding, we come to regard things as being or having characteristics that are really not there. For instance, to regard anything that is part of our individuality, or experience as something permanent, or something we have absolute and complete control over.
"for example, during the teaching session I was very hungry. I thought, "I can meditate and come to ignore how hungry I am- but if I did that every time, one day I would die of starvation, whether I was aware of that in my mind or not. So surely hunger is actually "real" and not just in my mind - because it will lead to me dying unnecessarily unless I react to it?""
This reflection is in accord with the words of the Buddha in the sutras. A similar analysis is used by Buddha to justify the conclusion that, say, "hunger" is not under one's complete and absolute control -- i.e., one cannot decide to not be hungry anymore, and have the wish granted.

Form is nonself. For if, bhikkhus, form were self, this form would not lead to affliction, and it would be possible to have it of form: ‘Let my form be thus; let my form not be thus.’ But because form is nonself, form leads to affliction, and it is not possible to have it of form: ‘Let my form be thus; let my form not be thus.’

Feeling is nonself. For if, bhikkhus, feeling were self, this feeling would not lead to affliction, and it would be possible to have it of feeling: ‘Let my feeling be thus; let my feeling not be thus.’

Perception is nonself. For if, bhikkhus, perception were self, this perception would not lead to affliction, and it would be possible to have it of perception: ‘Let my perception be thus; let my perception not be thus.’ [...]

Volitional formations are nonself. For if, bhikkhus, volitional formations were self, these volitional formations would not lead to affliction, and it would be possible to have it of volitional formations: ‘Let my volitional formations be thus; let my volitional formations not be thus.’ [...]

Consciousness is nonself. For if, bhikkhus, consciousness were self, this consciousness would not lead to affliction, and it would be possible to have it of consciousness: ‘Let my consciousness be thus; let my consciousness not be thus.’  [...]

The above are taken from SN 22.59.
"Another example I thought of was murder. I can believe everyone is neither good nor bad, and via compassion, everyone will seem good. But surely it doesn't matter how I imagine a situation is going in my mind - if I meet someone who tries to murder me, for example, they will kill me, regardless of how loving I believe them to be. My death would occur regardless of my mind (but if I had listened to my mind, I might have been able to avoid the death that would result from interacting with that person)."
Because of impermanence, it's fair to say that no one is good nor bad -- someone who was a "bad person" in the past might now be "a good person", and vice-versa. Or even, a person might have both inclinations.
The same statement about no one being good nor bad might have a deeper meaning -- when it is a statement about anatta (not self).
But no amount of compassion is sufficient to guarantee safety from physical harm. At least, the buddhist traditions I'm familiar with are in accord with this. I don't know about New Kadampa.
"I understand that death isn't "good" or "bad" either - but how does the dharma explain the division between "mind reality" and actual physical reality that can kill me no matter what my mind does?"
In the suttas, the Buddha says:

"Intention, I tell you, is kamma (action). Intending, one does kamma (action) by way of body, speech, & mind.
-- AN 6.63

So, by means of intention that "you" or "your mind" starts an act to affect "actual" reality.
And, in the words of the Buddha, how does actual reality affects "you" or "your mind"?

“[...] In dependence on the eye and forms, eye-consciousness arises. The meeting of the three is contact. With contact as condition, [pleasant, painful, neither] feeling comes to be; [...]"
-- SN 12.43

This is only an example of a process of cognition of something or an event in the actual reality, but the same applies to all of the senses.
In other words, because of the functioning of the sense organs (eye, ear, nose, etc) and the presence of what can be perceived by those (forms, sounds, tastes, temperature, pressure etc), it's possible to have cognition of an event in reality.
That's how, say, the perception of being killed in the actual reality becomes present.
"I also have a very similar question/example: why does it result in good karma when you feed starving people, if the food, the pain of starvation, and even your good deed is just an illusion in the minds of you and the starving person? Obviously if I had a sandwich, and I saw a child who was hungry, I'd give them all of the sandwich. But then isnt the child receiving negative karma for causing ME to go hungry, even though it was my choice? And why bother at all if only karma is real - the child's hunger isn't "real", so why end it?)"
Again, I don't where New Kadampa stands on this. Some buddhist traditions reject Idealism and some traditions accuse other traditions of the "mind only" view.
In any case, I think these questions that you raise are very significant to be asked to anyone before you decide to take their teachings.
Having said that, I'll take the liberty to answer the above from other buddhist perspectives.
First, a deed in many buddhist traditions is not completely evaluated by it's results (e.g. the food given satisfied someone's hunger, or money given was used to buy drugs). To a certain extent, it's evaluated by one's intention, motivation and attitude when performing it. To that extent, the deeds transforms one's inner habits, transforms one's minds (thoughts, reflexes, inclinations, tastes).
Thus, regardless of the actual results of the deeds, the performance of good deeds naturally turns one into a "good person", one who is inclined to have good thoughts (thoughts associated with non-hatred and non-greed), to associate with good people, inclined to do good. And bad deeds turns one into a "bad person", one inclined to do bad things, to take pleasure associating with bad people, to have bad thoughts associated with hatred and greed, etc.
So, an action, in this sense, is a way of transforming one's character, or one's mind. This is straightforward, and not really an understanding exclusive to Buddhism. Apparently, the following remarks come from Christians, but it's not at all far from what the Buddha taught:

The thought manifests as the word;
  The word manifests as the deed;
  The deed develops into habit;
  And habit hardens into character.

On the other hand, the effect of the deed and also to whom it benefits (or hurts) also comes into play in the theories of buddhist karma. But I think it's the perspective of transforming one's mind that gains more emphasis on the buddhist training.
The importance of doing good deeds in Buddhism is two-fold:

It affects the suffering one is subject to encounter in the future. In this current life, it makes one tolerate pain and unfortunate events easier. In future lives (if one takes it as true), it may lead one to more peaceful destinations, with less suffering.
It's transformative effect prepares the mind to take on deeper practices to understand the most subtle laws of reality.

My teacher has been talking about how each person's reality (including
  the body) is in fact an illusion generated by the mind in each moment

Your 'teacher' is wrong, with ideas that are not Buddhist.

As an extension of this, she teaches that there are no "good" or "bad"
  people

There are sets of aggregates with mental dispositions that predominantly perform harmless or violent actions, which are conventionally known as 'good & bad people'.
The ideas of 'good', 'bad' & 'person' are created by the mind however this does not change the nature of violence or harmlessness.

things or circumstances - the way things appear and the qualities they have are all coming from my own mind.

In Buddhism, actions based in greed, hatred & delusion are 'bad' or 'unwholesome' because they are destuctive. They do not come from your own mind but are universal realities.

I think I kind of understand this as a metaphor, but I don't understand how she can seem to literally believe this: for example,
  during the teaching session I was very hungry. I thought, "I can
  meditate and come to ignore how hungry I am- but if I did that every
  time, one day I would die of starvation, whether I was aware of that
  in my mind or not. So surely hunger is actually "real" and not just in
  my mind - because it will lead to me dying unnecessarily unless I
  react to it?"

Hunger is created by the biological mechanisms of the physical body, which creates hunger pain. If the mind chooses to starve to death, the hunger pain will exist until death. Thus, the hunger is not created by the mind. It is created by the body.

Another example I thought of was murder. I can believe everyone is neither good nor bad, and via compassion, everyone will seem good. But
  surely it doesn't matter how I imagine a situation is going in my mind
  - if I meet someone who tries to murder me, for example, they will kill me, regardless of how loving I believe them to be. My death would
  occur regardless of my mind (but if I had listened to my mind, I might
  have been able to avoid the death that would result from interacting
  with that person).

The Buddha taught greed, hatred & delusion are 'the unwholesome', i.e., 'destructive'. If the mind is enlightened, it will not have the view of "I am dying". However, the murderous actions remain destructive.

I understand that death isn't "good" or "bad" either - but how does the dharma explain the division between "mind reality" and actual
  physical reality that can kill me no matter what my mind does?

The dharma states all conditioned things are impermanent & this impermanence is unrelated to mental cognition. This is why your teacher is wrong.

Another quick example: medication for mental illness. I had a teacher once who endorsed mentally ill people stopping all medication, because
  it was only a placebo - but if that's true then why is it that an
  unmedicated schizophrenic (for example) would be physically unable to
  meditate (and cure themselves, as my teacher suggested) most of the
  time, as they would be too ill to concentrate? Isnt that an example of
  physical chemicals (drugs) being "stronger" than the mind (calming the
  mind so that it can begin to meditate)?

Yes. What you wrote is correct. That chemicals have powerful effects upon the mind shows the mind does not create the entire reality.

(Edit: I also have a very similar question/example: why does it result in good karma when you feed starving people, if the food, the
  pain of starvation, and even your good deed is just an illusion in the
  minds of you and the starving person?

A good deed may be an illusion but doing good deeds develops virtue. The path is threefold, namely, virtue, meditation, wisdom.

Obviously if I had a sandwich, and I saw a child who was hungry, I'd give them all of the sandwich. But then isnt the child receiving
  negative karma for causing ME to go hungry, even though it was my
  choice?

No. Karma is intention. It was your intention to give your sandwich away therefore it was your intention that causes your own hunger.

And why bother at all if only karma is real - the child's hunger
  isn't "real", so why end it?)

There are two-levels of dharma. Karma is the moral level & the foundation for the higher level. For example, doing bad karma creates hindrances to concentration, which will be a hindrance to realising the 'illusory' nature of the 'self' fabrication. To reach the higher level of enlightenment, bad karma must be avoided.

We don't need to eat, we assume we need to eat.  All concepts words, ideas, reason, logic are all human assumptions. Real  experiential reality doesn't admit of any person's concepts. We don't have to ponder anything but naked reality. Just witness what arises and falls through your eyes, ears, tongue, body sensation, partiality, emotions and thoughts(just the thought not it's conceptual contents) and insights will come subtly and grossly. Naked reality, naked truth, naked experience, empty experience and many more sayings mean reality without our categorization of everything. It's experiencing what is in our awareness on a moment to moment basis.

@no comprende The practice of not practicing and just staying in our comfort zones is how we are like animals.

My teacher has been talking about how each person's reality ... the way things appear and the qualities they have are all coming from my own mind.
What decides wholesome and unwholesome is why and how we react when we experience the result. Generally you receive what you give. For this reason, give what you want to expect.
... food ...
To sustain life you need 4 inputs

Edible food, coarse and fine;
  secondly, sense-impression;
  thirdly, volitional thought;
  fourthly, consciousness.

Puttamansa Sutta
If you were to "fast" or "starve" at all, you should starve yourself of new Karma producing activity (volitional thought) by being equanimous [and seeing impermanence], rather than reduce edible food to unhealthy levels.
As for edible food you should take timely and adequate amount of food to sustain life and you meditation practice.
... I understand that death isn't "good" or "bad" either ...
Death is not good or bad. It is the intention. If you intend to harm this is unwholesome and then you experience the results you will not like it.
Say a surgeon does a operation to save a life but the patient dies the intention was good hence this is good.
If a mugger kills to snatch a purse, then the intention is bad so the karmic result will be unfavorable.
Finally what you practice and believe in should lead to the benefit of oneself and that of others. Always see if it is this belief or practice is to my benefit and that of others and embrace it. If not, leave it aside. The benefits should be tangible which you experience here and now.

How does what your teacher is telling you help you? Does it help you to live your life better? To let go? To experience more freedom and happiness?  To show up more for others with generosity and compassion? Is what they are teaching you useful? Or is it all just a bunch of meaningless mystical jargon that leads to confusion and has no real practical bearing on your reality?  This is what you might ask yourself.
It's true that everything that happens we experience through a filter of our own conditioning and history etc. for example when we see an animal such as a lion kill another animal we accept that it's just normal because this is what they must do to survive. However when we see a human take another human life we see it through a whole bunch of concepts that have been fed into our minds by our culture.
Also we seem to have no problem with mass factory farming animals in the most abhorrent conditions so that we can have a nice piece of flesh to eat all packed cleanly and neatly on the supermarket shelf. When you think about what actually happens to those animals it's nothing short of a horrifying tragedy yet we can just compartmentalise and deny it all while we eat our meat in a detached way around the bbq with friends.  Surely killing millions of animals cruelly and unnecessarily, because after all we don't need to eat meat, is far worse than one person killing one other person? But we do not believe this so for us it is not true.  If a woman kills her abusive husband to save her own life and or her children's lives we would have no problem with it.
Another example is the way terrorism is viewed in Western cultures. As horrifying as it is, we are manipulated by our politicians who feed us a very biased narrative about it on one hand and on the other are waging war and killing millions of innocent people.
So in the end it's always about your beliefs and concepts that make something good or bad, right or wrong.
If you think about your mentioned thoughts on hunger. Hunger itself does not exist. What exists is a naked sensation in the body. We add the idea or concept called "hunger" to it. We have been conditioned that when I feel this it means I must eat. When you were a baby it didn't mean the same thing, it was just discomfort and you reacted to it by crying then your mother fed you. So in this sense hunger does not exist. It's not that things don't exist, it's that they are not what you believe them to be.

Very true. Whether illusion or real, what gives out what comes back, it's the law. The Buddhist teaching said, the wars are the (karmic) response to killing, whether killing animals or humans. Mahayanist doctrine is to abstain from meat.

It is not that each person's ego is making the reality but that the Mind is creating the reality.
Hence, the rules that have come out of that are in effect.
Even without Enlightenment though there are ways to go beyond hunger e.g. eating chi.
But once Enlightened, one can change those rules--not that one would really care to doctor reality.

It's dangerous and the beginning of suffering when our mind and our intellect goes in split, our prime evil in the 12 Nidanas begin with Ignorance. That's why when our intellect knew reality is mind created, but our mind can't see the real reality. Thus the rest of your analogies in your questions are the declarations of the intellect, but the mind doesn't agree to see the same. So they are fallacies, but correct in terms of clauses written on the human laws books. Your teacher taught a very dangerous teaching. The battle between Emptiness空 and Beingness有 was quite bloody in the history of Tibetan Buddhism. Some Bhikkhus committed gravely sins when caught up by the notion of Emptiness, with only their intellectual understanding.
If we need to eat "food" to survive or not for reality is mind created. In fact, what do you think that is "food"? When broken down into smaller and smaller units, food is just energy. A grain of rice is full of carbon, so is charcoal, diamond, but you can't eat diamond can you? The Buddha said all are combinations of the 4 Greats (attributions): fire water earth wind, plus 3 more totaled 7 Greats but they are not directly involved in forming "matter". In real there are no such things as apple, potato, cabbage... etc. If your mind and intellect are "coherent", yes, eating is no longer corresponding to human food only. In Chinese self-cultivation practice 辟谷, abstain of human food, is a very common practice. This is also likely known in traditional Indian yogis. Practicing meditation there are ways to intake energy directly from the surrounding. In fact, to a deeper level, this intake-release of energy is also an illusion. However, if your mind can't directly see the illusion, only your intellect is babbling, this won't have any effect on actual feeling the hunger, and eventual starve to death. :\

Nine other answers have directly addressed your question, so I will take a different route: explaining that the premise is incorrect, as you have already suspected. Perhaps this will be useful to you.
Ideas of the kind you say your teachers are putting forth amount to this core concept: There is something beyond the material reality that we see.

This is not a Buddhist idea, so these people are not teaching Buddhism, they are teaching something that they have added on to it.
All such claims are subjective and completely unverifiable, so they are not knowledge.
Whether right or wrong, they are not teachable information. It is not reliably possible to induce awareness or an experience in another person.

There might be more that I could add, but it is sufficient to be able to dismiss such ideas as not necessary to the path (any path). They can only be seen as one person's impression. If they are disseminated as teaching, they must be regarded as dogma.
I would hand them a copy of the Heart Sutra and move on. As Gary Zukav summarized: "That which is, is that which is." We are all individually responsible for holding fast to this and to not accept teachings of alternative realities.


text:
Abhava versus Vibhava
Is there a difference between abhava and vibhava? Or are those words synonyms?
When they are not synonyms, what is their exact meaning.

Where exactly did you read about 'abhava'? Thanks. Is abhava from Hinduism https://en.wikipedia.org/wiki/Abhava or from Buddhism?

Indeed, I found it in the Upanishads.

'Vibhava' is a form of 'becoming' or 'self-view', namely, the idea "I do not exist" or "I do not want to exist" or "I will cease to exist". Since the idea of 'I' ('atta') or "a being/person" ('satta') still remains, 'vibhava' is a type of becoming (bhava). This is described in the following suttas:

Tayidaṃ, bhikkhave, tathāgato abhijānāti. Ye kho te bhonto samaṇabrāhmaṇā sato sattassa ucchedaṃ vināsaṃ vibhavaṃ paññapenti
  te sakkāyabhayā sakkāyaparijegucchā sakkāyaññeva
  anuparidhāvanti anuparivattanti. Seyyathāpi nāma sā gaddulabaddho
  daḷhe thambhe vā khile vā upanibaddho, tameva thambhaṃ vā khilaṃ vā
  anuparidhāvati anuparivattatianuparivattati evamevime bhonto
  samaṇabrāhmaṇā sakkāyabhayā sakkāyaparijegucchā sakkāyaññeva
  anuparidhāvanti anuparivattanti.
Those recluses that describe the annihilation, destruction & extermination (vibhavaṃ; non-existence) of an existing being (sattassa);
  through fear & disgust with identity (sakkāya), keep running &
  circling around that same identity; just as a dog bound by a leash to
  a post keeps running & circling around that same post....
MN 102.12

Kathañca, bhikkhave, atidhāvanti eke? Bhaveneva kho paneke aṭṭīyamānā harāyamānā jigucchamānā vibhavaṃ abhinandanti—yato kira, bho, ayaṃ
  attā kāyassa bhedā paraṃ maraṇā ucchijjati vinassati na hoti paraṃ
  maraṇā; etaṃ santaṃ etaṃ paṇītaṃ etaṃ yāthāvanti. Evaṃ kho, bhikkhave,
  atidhāvanti eke.
How, bhikkhus, do some overreach? Now some are troubled, ashamed and disgusted by this very same being and they rejoice in (the idea of)
  non-being, asserting: ‘In as much as this self, good sirs, when the
  body perishes at death, is annihilated and destroyed and does not
  exist after death—this is peaceful, this is excellent, this is
  reality!’ Thus, bhikkhus, do some overreach.
Iti 44

As for 'abhava', I do not currently know what it means in Pali Buddhism.
'Abhava' appears to not have the same meaning as 'abhavissā', which seems to mean: 'if was' or 'would have been', as found in the 2nd sermon:

Rūpañca hidaṃ, bhikkhave, attā abhavissa, nayidaṃ rūpaṃ ābādhāya saṃvatteyya
For if, bhikkhus, form were self, this form would not lead to affliction...

'Vibhava' is not a synonym for Nibbana or the Unconditioned. MN 140 states:

So nevaneva taṃ abhisaṅkharoti, na abhisañcetayati bhavāya vā vibhavāya vā. So anabhisaṅkharonto anabhisañcetayanto bhavāya vā
  vibhavāya vā na kiñci loke upādiyati, anupādiyaṃ na paritassati,
  aparitassaṃ paccattaṃyeva parinibbāyati
He does not form any condition or generate any volition tending towards either being or non-being. Since he does not form any
  condition or generate any volition tending towards either being or
  non-being, he does not cling to anything in this world. When he does
  not cling, he is not agitated. When he is not agitated, he personally
  attains Nibbāna.

In Hinduism, 'abhava' appears to refer to a primordial unconditioned state, namely, unmanifest level from where the concrete bhava arises or emerges.
'Abhava' here, in Hinduism, is not a synonymous with 'vibhava' in Buddhism because, in Buddhism, 'bhava' ('becoming') must occur before 'vibhava' can occur.
The idea of 'I' is 'bhava'. The idea of "I" must exist before the idea of "I do not want to exist" can occur. For example, the idea of "I", "me" or "self" must occur before the wish to commit suicide.

Let's assume that bhava means "existence".
I think that the a prefix means "not" (it appears in a lot of Buddhist words, like anatta and so on).
I think that the vi prefix might mean "the reverse of" (see e.g. the dictionary definition quoted here).
So my guess is that abhava means "non-existence", whereas vibhava means "destruction".
The phrase vibhavataṇhā is used in the definition of the second noble truth in SN 56.11, so you can read various translations of vibhava in the various translations of that sutta, for example:

craving for extermination (of what is not liked)
craving for non-being
craving for non-existence (self-annihilation)
craving for non-becoming
craving for non-existence [for extinction].

The first translation of SN 56.11 that I read translated bhavataṇhā and vibhavataṇhā as "the craving to live and even the craving to die", so that's the way I remember it.
In summary, maybe they mean the same thing (i.e. "non-existence"); but if they aren't synonyms, then one simply means "non-existence" and the other implies a "transition from existence to non-existence" for example "annihilation, destruction, extinction, death".

'Vibhava tanha' refers to any craving not-to-be, such as not wanting to be in the hot sun. Its application is far broader than merely not wanting to live. Regards

@Dhammadhatu Your example of not wanting to be in the hot sun is interesting. I am not sure if you can use it to describe vibhavataṇhā, because being in the hot sun is a sensory experience, so I would naively say it's more an example of kamataṇhā. Does kamataṇhā also include disliking/aversion to sensory objects?

@OidaOudenEidos The question "Could Lobha(craving) and Dosa(aversion) be working in tandem?" says that "wanting pain to disappear" or "desire for the non painful state" is 'Vibhava tanha'.

@OidaOudenEidos No. Aversion to the hot sun is not kamatahna since the suttas define this as craving for what is pleasing. To quote: "There are, monks, these five strings of sensuality. Which five? Forms cognizable via the eye — agreeable, pleasing, charming, endearing, fostering desire, enticing." ...Every form of craving must fall within the three kinds of craving in the 2nd noble truth. Regards

@Dhammadhatu So any form of disliking falls under vibhava tanha? @ChrisW Thanks for the reference.

I suppose so. I prefer to translate vibhava tanha as 'craving-not-to-be'. Regards

I recently stumbled upon an interesting explanation of vibhavataṇhā in the german translation of the Majjhima Nikāya by Mettiko Bhikkhu. I tried to translate this explanation as good as I could into english. The following is from page 25 (3rd edition, 2014):

Bhavataṇhā generally is craving for being, or in a more precise case the craving for being in the current, present situation.
Vibhavataṇhā often is misunderstood as craving for non-existence. That is linguistcally wrong, because the prefix "vi-" does not mean "not", but it means "different than, dis-, apart-, parallel to". (A-bhava, not-becoming/non-existence only occurs very rarely in the texts and in different contexts.) Furthermore would "craving for non-existence" mean, that the Buddha teaches a fundamental category, which only applies to specific people at a specific times -- a contradiction in terms, which is not consistent with the spirit/tenor of the Suttas.
From an existential point of view it's also impossible to imagine "non-existence/being" or to wish it. Even a potential suicide does not wish for 'nothing', but rather for 'something else'.
Vibhavataṇhā is a potential/possible existence/state of being, which we use to isolate and define our present existence/state of being, regardless of whether these possibilities are going to become true or not. Just as it only makes sense to speak about the color red when there are things that are not red, our existence becomes established by the possibilities that we have within it (or around it). An example: How often do we speak while eating about different food or things we ate in the past or might eat in the future, even if the present meal is 100% satisfying?
That's why I'll translate Vibhavataṇhā as "Craving for potential existence", the craving for a background for the own existence. The philosophical fun question "Life is strange ... compared to what?" therefore is not far fetched.
This kind of craving is one of the three forms of the source of a relative, conditioned personality (sakkāya) as it is described in the teachings of the Buddha (for example in M44). Follower of other teachings that don't base on conditions, postulate the existence of an absolute, permanent, independent self. In their language, referring to an absolute self, the sense of "being-different-than" (Vibhavataṇhā) can of course only mean annihilation and in these cases is also translated as such, as well as when the Buddha talks about the standpoint of those teachings (i.e. M102).

I might adjust/refine the translation, if there is some feedback. But for now, I hope a sloppy (sometimes word by word) translation is enough.
In summary, what this section says is that Vibha within the Buddha's teaching can mean two things:

non-existence, if a different philosophy or teaching is addressed, which states a permanent self.
Craving to be different, become somebody else (Which I think is what is meant by "craving for potential existence").

Vibhava means disbelief in rebirth. Vibhava is always gets referred to with “tanha”. Tanha is “getting attached to things in this world” via greed, hate, and ignorance. Vibhava tanha then can be taken as "getting attached to non-existence" or that nothing exists after death. This view arises from the wrong view of materialism. In Pali it is called ucceda ditthi. One believes that at death one ceases to exist, i.e., one believes that the mind is a by-product of the body (brain), and thus when the body dies, that is the end of story. Thus one believes that one needs to just enjoy the pleasures of this life before dying as nothing exists after death.
It is easy to have ucceda ditthi and vibhava tanha, especially when one has not heard about the Buddha’s message about a wider and more complex world with 31 realms and a rebirth process. Since our normal human senses cannot access such “hidden” aspects of this world, one just believes what one sees. It takes a wider world view to explain such & in not seeing the truth, many immoral acts are done with ucceda ditthi (or materialism or nihilism) because one believes that everything in this world is for one’s enjoyment.
Abhava and Vibhava are two different words. Abhava means a death of a person or being. On the other hand Vibhava can have some relation to “antarabhava“ - “antara-bhava“ – an in-between zone from one bhava to another.  It is the Mahayanists who coined this term and started saying that there is an antarabhava. But at the Third Buddhist Council, this was proved wrong and that there is no antarabhava.

Where do the suttas state vibhava means disbelief in rebirth? Thanks

Going forward I will try to show another way of seeing/interpreting a given word. This is one attempt towards  it. As per your question... It is in the Brahmajala sutta: https://suttacentral.net/pi/dn1
in section 3.2.4. Ucchedavada section - . Vibhava tanha arises from ucceda ditthi.

This does not show anything because 'vibhava' is a self-view; just as ucceda ditthi is a self-view. Please read carefully. Each quote in the suttas states a 'self' or 'being' is annihilated. I will wrote an answer to explain.

@Dhammadhatu.. it is quite clear that vibhava tanha is associated with ucceda ditthi, the view that one lives just this life and that is the end of it. So, one tries to "enjoy life to the fullest" until death. Also, one may have more than one ditthi. There are so many interpretations of "self view". Are you reading the Pali, or English, version of the sutta?

Please do not make pointless comments towards me. You are posting 'eternalism'. You do not understand the teachings. Both eternalism & nihilism are 'self-views'. They both contain the belief about a 'self'. Thanks