What is an overview of Christian viewpoints on what happens to humans after death? My (rather superficial) understanding is that most Christians would agree that human beings are composed of body, spirit and soul. Now, I'm aware that the terms &quot;soul&quot; and &quot;spirit&quot; can be a little bit confusing, that some would claim that there is only &quot;body&quot; and &quot;spirit&quot; and that &quot;spirit&quot; and &quot;soul&quot; are just synonymous, etc. To be honest, my understanding of these terms is not particularly the strongest.
That said, at the moment of death, something happens to this union of body, soul and spirit (whatever these terms mean). With regard to the body, I would expect everyone to agree that it decomposes and turns into dust -- at least this much shouldn't be controversial. But what about the soul and the spirit? Do soul and spirit stay together after death or do they part ways too? And where do they go? And what about a person's consciousness? Are they still conscious or in deep sleep, waiting for the resurrection of the body? And what about their ability to communicate? Can the dead communicate with each other? Can the dead communicate with the living?
As you see, tons of questions can be asked, but I think they can be summarized in a single question: what happens (or can happen) to people once they die?
Since answers are obviously dependent on the particular beliefs of each denomination, I'm interested in an overview of the main Christian viewpoints regarding these questions. References to the biblical basis of each view will be appreciated as well.
What is an overview of Christian viewpoints on what happens to humans after death?
Catholicism

Individual eschatology
Death
Death, which consists in the separation of soul and body, is presented under many aspects in Catholic teaching, but chiefly

as being actually and historically, in the present order of supernatural Providence, the consequence and penalty of Adam's sin (Genesis 2:17; Romans 5:12, etc.);

as being the end of man's period of probation, the event which decides his eternal destiny (2 Corinthians 5:10; John 9:4; Luke 12:40; 16:19 sqq.; etc.), though it does not exclude an intermediate state of purification for the imperfect who die in God's grace; and

as being universal, though as to its absolute universality (for those living at the end of the world) there is some room for doubt because of 1 Thessalonians 4:14 sqq.; 1 Corinthians 15:51; 2 Timothy 4:1.


Particular Judgment
That a particular judgment of each soul takes place at death is implied in many passages of the New Testament (Luke 16:22 sqq.; 23:43; Acts 1:25; etc.), and in the teaching of the Council of Florence (Denzinger, Enchiridion, no. 588) regarding the speedy entry of each soul into heaven, purgatory, or hell.
Heaven
Heaven is the abode of the blessed, where (after the resurrection with glorified bodies) they enjoy, in the company of Christ and the angels, the immediate vision of God face to face, being supernaturally elevated by the light of glory so as to be capable of such a vision. There are infinite degrees of glory corresponding to degrees of merit, but all are unspeakably happy in the eternal possession of God. Only the perfectly pure and holy can enter heaven; but for those who have attained that state, either at death or after a course of purification in purgatory, entry into heaven is not deferred, as has sometimes been erroneously held, till after the General Judgment.
Purgatory
Purgatory is the intermediate state of unknown duration in which those who die imperfect, but not in unrepented mortal sin, undergo a course of penal purification, to qualify for admission into heaven. They share in the communion of saints and are benefited by our prayers and good works (see PRAYERS FOR THE DEAD). The denial of purgatory by the Reformers introduced a dismal blank in their eschatology and, after the manner of extremes, has led to extreme reactions.
Hell
Hell, in Catholic teaching, designates the place or state of men (and angels) who, because of sin, are excluded forever from the Beatific Vision. In this wide sense it applies to the state of those who die with only original sin on their souls (Council of Florence, Denzinger, no. 588), although this is not a state of misery or of subjective punishment of any kind, but merely implies the objective privation of supernatural bliss, which is compatible with a condition of perfect natural happiness. But in the narrower sense in which the name is ordinarily used, hell is the state of those who are punished eternally for unrepented personal mortal sin. Beyond affirming the existence of such a state, with varying degrees of punishment corresponding to degrees of guilt and its eternal or unending duration, Catholic doctrine does not go. It is a terrible and mysterious truth, but it is clearly and emphatically taught by Christ and the Apostles. Rationalists may deny the eternity of hell in spite of the authority of Christ, and professing Christians, who are unwilling to admit it, may try to explain away Christ's words; but it remains as the Divinely revealed solution of the problem of moral evil. (See HELL.) Rival solutions have been sought for in some form of the theory of restitution or, less commonly, in the theory of annihilation or conditional immortality. The restitutionist view, which in its Origenist form was condemned at the Council of Constantinople in 543, and later at the Fifth General Council is the cardinal dogma of modern Universalism, and is favoured more or less by liberal Protestants and Anglicans. Based on an exaggerated optimism for which present experience offers no guarantee, this view assumes the all-conquering efficacy of the ministry of grace in a life of probation after death, and looks forward to the ultimate conversion of all sinners and the voluntary disappearance of moral evil from the universe. Annihilationists, on the other hand, failing to find either in reason or Revelation any grounds for such optimism, and considering immortality itself to be a grace and not the natural attribute of the soul, believe that the finally impenitent will be annihilated or cease to exist — that God will thus ultimately be compelled to confess the failure of His purpose and power. - Eschatology (Catholic Encyclopaedia)

The Catholic Church holds that &quot;all who die in God's grace and friendship but still imperfectly purified&quot; undergo the process of purification which the Church calls purgatory, &quot;so as to achieve the holiness necessary to enter the joy of heaven&quot;. It bases its teaching also on the practice of praying for the dead, in use within the Church ever since the Church began, and mentioned in the deuterocanonical book 2 Maccabees 12:46.2
Limbo of Infants

On 20 April 2007, the advisory body known as the International Theological Commission released a document, originally commissioned by Pope John Paul II, entitled &quot;The Hope of Salvation for Infants Who Die without Being Baptized.&quot; After tracing the history of the various opinions that have been and are held on the eternal fate of unbaptized infants, including that connected with the theory of the Limbo of Infants, and after examining the theological arguments, the document stated its conclusion as follows:
Our conclusion is that the many factors that we have considered above give serious theological and liturgical grounds for hope that unbaptized infants who die will be saved and enjoy the beatific vision. We emphasize that these are reasons for prayerful hope, rather than grounds for sure knowledge. There is much that simply has not been revealed to us.[33] We live by faith and hope in the God of mercy and love who has been revealed to us in Christ, and the Spirit moves us to pray in constant thankfulness and joy.
What has been revealed to us is that the ordinary way of salvation is by the sacrament of baptism. None of the above considerations should be taken as qualifying the necessity of baptism or justifying delay in administering the sacrament. Rather, as we want to reaffirm in conclusion, they provide strong grounds for hope that God will save infants when we have not been able to do for them what we would have wished to do, namely, to baptize them into the faith and life of the Church.
Pope Benedict XVI authorized publication of this document, indicating that he considers it consistent with the Church's teaching, though it is not an official expression of that teaching. Media reports that by the document &quot;the Pope closed Limbo&quot; are thus without foundation. In fact, the document explicitly states that &quot;the theory of limbo, understood as a state which includes the souls of infants who die subject to original sin and without baptism, and who, therefore, neither merit the beatific vision, nor yet are subjected to any punishment, because they are not guilty of any personal sin. This theory, elaborated by theologians beginning in the Middle Ages, never entered into the dogmatic definitions of the Magisterium. Still, that same Magisterium did at times mention the theory in its ordinary teaching up until the Second Vatican Council. It remains therefore a possible theological hypothesis&quot; (second preliminary paragraph); and in paragraph 41 it repeats that the theory of Limbo &quot;remains a possible theological opinion&quot;. The document thus allows the hypothesis of a limbo of infants to be held as one of the existing theories about the fate of children who die without being baptised, a question on which there is &quot;no explicit answer&quot; from Scripture or tradition. The traditional theological alternative to Limbo was not Heaven, but rather some degree of suffering in Hell. At any rate, these theories are not the official teaching of the Catholic Church, but are only opinions that the Church does not condemn, permitting them to be held by its members, just as is the theory of possible salvation for infants dying without baptism. - Limbo (Wikipedia)

Benedict XII (reigned 1334-1342) declared the following dogma in Benedictus Deus (1336):

We define that according to the general disposition of God, the souls of those who die in actual mortal sin go down into hell immediately (mox) after death and there suffer the pain of hell.

Orthodoxy

God created us for life; it is not His will that we die. Death was not intended for us, not willed by God. It is, as St. Paul says, “the last enemy”. Death is a rebellion against God. It came into the world because the first man and woman chose death, darkness, and themselves over God. Because of sin, death entered this world. And we are all affected by the consequence (death) of Adam and Eve’s sin in Paradise.
When we die, our souls separate from our bodies. After this separation, the body then returns to the earth and, eventually, decomposes. But what happens after that?
Between the moment of our death and the Final Judgment (more on this shortly), the soul lives in a “middle state” and undergoes what we call the particular judgment (Hebrews 9:27). In other words, immediately after death, we experience a foretaste of paradise or hell, depending on the kind of life we lived here on earth. And our souls remain in this state until the Final Judgment, when all will “come forth – those who have done good, to the resurrection of life, and those who have done evil, to the resurrection of condemnation” (John 5:28-29).
The Final Judgement
At the Final Judgment, our souls will be reunited with our bodies, and both will be judged before God (2 Corinthians 5:10). We will be judged according to our faith and our works (the fruits of faith).
God will separate the just from the unjust or sinners. To the righteous He will say, “Come, O blessed of my Father, inherit the kingdom prepared for you from the foundation of the world” (Matthew 25:34). And to the sinners: “Depart from me, you cursed, into the eternal fire prepared for the devil and his angels” (Matthew 25:41). Then, the sinners “will go away into eternal punishment, but the righteous into eternal life” (Matthew 25:46).
After the Final Judgement, there is either eternal life or eternal punishment. Which one, depends entirely on us and the kind of lives we live. Think of it this way. When we’re born into this world, it’s like having bad vision. Nothing is clear. When we become Orthodox and meet Christ, we’ve just received a pair of glasses. Things clear up, but we keep getting the lenses dirty. The sacraments are God’s way of helping us clean our glasses, over and over again. When we die, we’ll finally see God clearly and will have no need for our glasses anymore. And we will either rejoice in finally seeing Him clearly (if that was our goal in this life) or our eyes will hurt with the sudden vision of light after being so long in the dark. We will experience His presence as either absolute bliss or unbearable agony, for eternity.
What About Purgatory?
Some Church Fathers, including St. Cyprian and St. Augustine, seemed to believe in a purification after death. However, the character of this purification is never clarified, and (as St. Mark of Ephesus underlined at the Council of Florence) it seems there is no true distinction between heaven, hell and the so-called purgatory. In other words, all souls partake in the same mystical fire (which, according to St. Isaac of Syria, is God’s Love), but experience it differently depending on their spiritual state: bliss for those who are in communion with him; purification for those in the process of being deified; and remorse/agony for those who hated God during their earthly lives. - What Happens When We Die?

Protestantism

For Protestants this life is a pilgrimage, a journey toward an eternal destination. That destination is an eternity spent either in heaven or in hell. Those saved enjoy some benefits here on earth during their pilgrimage. Salvation is not just an experience for the afterlife; it involves the &quot;first fruits&quot; of blessedness, that is, a proper relationship with God, a gradual transformation into the likeness of Christ, and the filling of the Holy Spirit. This process will not be complete, however, in this life.
Some Protestants hold that there is nothing one can do to earn a spot in heaven; God freely chooses to forgive the sins of some, and they can enter heaven.  Others hold that though forgiveness is only possible through God's grace, it is offered to all and anyone can freely accept this forgiveness.  These Protestants, who endow humans with some degree of free will and some responsibility for effecting their own salvation, tend also to believe that one's ultimate fate rests to some extent on one's works—both in actively choosing God through faith, and in a life of growing conformity to the teaching of Christ.
Because purgatory is not explicitly mentioned in the Bible, nearly all Protestants reject the Roman Catholic teaching that there is also a transitional place or process of purification of the soul after death. That said, there is some diversity of thought about what happens immediately after death. While nearly all Protestants believe that the individual retains its unique identity after death (unlike Eastern religions), some believe that the soul goes immediately to be with Christ in heaven, awaiting the Day of Judgment and a resurrected body. Others suggest that there is an intermediate time of &quot;soul sleep,&quot; an unconscious waiting for the resurrection. Some believe that the souls of the dead proceed immediately on death either to heaven or hell. Still others argue that the temporality of this life versus the eternality of the life to come makes intermediate periods of time meaningless altogether.
Traditionally Protestants believe in a judgment day at the end of history. On this day all the dead from throughout human history will be resurrected, and will possess some sort of physical body that will resemble but yet be different from the body possessed during their earthly existence. Jesus' resurrection, described in all four Gospels, is the basis for this belief, and the apostle Paul emphasizes the resurrection, linking Christ's resurrection to the experience believers will have at the end of time. Paul insists that without the resurrection, Christian faith is meaningless (1 Cor. 15:12-19). At the final resurrection of the dead, the saints (or, the elect) enter heaven, while the damned are sent to hell. Heaven is a state of blessedness in the presence of God, something humans have not been able to experience since the fall in the Garden of Eden. Hell is a place of torment, as just punishment for sin. - Afterlife and Salvation

The Church of Jesus Christ of Latter-day Saints

When the physical body dies, the spirit continues to live. In the spirit world, the spirits of the righteous “are received into a state of happiness, which is called paradise, a state of rest, a state of peace, where they shall rest from all their troubles and from all care, and sorrow” (Alma 40:12). A place called spirit prison is reserved for “those who [have] died in their sins, without a knowledge of the truth, or in transgression, having rejected the prophets” (Doctrine and Covenants 138:32). The spirits in prison are “taught faith in God, repentance from sin, vicarious baptism for the remission of sins, the gift of the Holy Ghost by the laying on of hands, and all other principles of the gospel that [are] necessary for them to know” (Doctrine and Covenants 138:33–34). If they accept the principles of the gospel, repent of their sins, and accept ordinances performed in their behalf in temples, they will be welcomed into paradise.
Because of the Atonement and Resurrection of Jesus Christ, physical death is only temporary: “As in Adam all die, even so in Christ shall all be made alive” (1 Corinthians 15:22). Everyone will be resurrected, meaning that every person’s spirit will be reunited with his or her body—“restored to their proper and perfect frame” and no longer subject to death (Alma 40:23; see also Alma 11:44–45). - Death, Physical (Overview)
Spirit World
The postmortal spirit world is a place where the spirits of those who have died live before the Resurrection. The spirit world consists of paradise, where the righteous dwell, and spirit prison, where those who were wicked in mortality dwell.
Overview
The postmortal spirit world is a place where the spirits of those who have died live before the Resurrection. The spirit world consists of paradise, where the righteous dwell, and spirit prison, where those who were wicked in mortality dwell.
President Brigham Young taught that the postmortal spirit world is on the earth, around us (see Teachings of Presidents of the Church: Brigham Young [1997], 279).
Spirit beings have the same bodily form as mortals except that the spirit body is in perfect form (see Ether 3:16). Spirits carry with them from earth their attitudes of devotion or antagonism toward things of righteousness (see Alma 34:34). They have the same appetites and desires that they had when they lived on earth. All spirits are in adult form. They were adults before their mortal existence, and they are in adult form after death, even if they die as infants or children (see Teachings of Presidents of the Church: Joseph F. Smith [1998], 131–32).
The prophet Alma in the Book of Mormon taught about two divisions or states in the spirit world.
Paradise. According to the prophet Alma, the righteous spirits rest from earthly care and sorrow. Nevertheless, they are occupied in doing the work of the Lord. President Joseph F. Smith saw in a vision that immediately after Jesus Christ was crucified, He visited the righteous in the spirit world. He appointed messengers, gave them power and authority, and commissioned them to “carry the light of the gospel to them that were in darkness, even to all the spirits of men” (Doctrine and Covenants 138:30).
The Church is organized in the spirit world, and priesthood holders continue their responsibilities there (see Doctrine and Covenants 138:30). President Wilford Woodruff taught: “The same Priesthood exists on the other side of the veil. … Every Apostle, every Seventy, every Elder, etc., who has died in the faith as soon as he passes to the other side of the veil, enters into the work of the ministry” (Deseret News, Jan. 25, 1882, 818).
Spirit Prison. The Apostle Peter referred to the postmortal spirit world as a prison, which it is for some (see 1 Peter 3:18–20). In the spirit prison are the spirits of those who have not yet received the gospel of Jesus Christ. These spirits have agency and may be enticed by both good and evil. The spirits may progress as they learn gospel principles and live in accordance with them. The spirits in paradise can teach the spirits in prison (see Doctrine and Covenants 138). If they accept the gospel and the ordinances performed for them in the temples, they may leave the spirit prison and dwell in paradise.
Also in the spirit prison are those who rejected the gospel after it was preached to them either on earth or in the spirit prison. These spirits suffer in a condition known as hell. They have removed themselves from the mercy of Jesus Christ, who said, “Behold, I, God, have suffered these things for all, that they might not suffer if they would repent; but if they would not repent they must suffer even as I; which suffering caused myself, even God, the greatest of all, to tremble because of pain, and to bleed at every pore, and to suffer both body and spirit” (Doctrine and Covenants 19:16–18). After suffering for their sins, they will be allowed, through the Atonement of Jesus Christ, to inherit the lowest degree of glory, which is the Telestial kingdom. - Spirit World

Jehovah's Witness

The Bible says: “The living are conscious that they will die; but as for the dead, they are conscious of nothing at all.” (Ecclesiastes 9:5; Psalm 146:4) Therefore, when we die, we cease to exist. The dead can’t think, act, or feel anything.
“To dust you will return”
God explained what happens when we die when he spoke to the first man, Adam. Because Adam was disobedient, God said to him: “Dust you are and to dust you will return.” (Genesis 3:19) Before God created Adam “out of dust from the ground,” Adam did not exist. (Genesis 2:7) Likewise, when Adam died, he returned to dust and ceased to exist.
The same thing happens to those who die now. Speaking of both humans and animals, the Bible says: “They have all come to be from the dust, and they are all returning to the dust.” ​— Ecclesiastes 3:19, 20.
Death is not necessarily the end of everything
The Bible often compares death to sleep. (Psalm 13:3; John 11:11-14; Acts 7:60) A person who is fast asleep is unaware of what is happening around him. Likewise, the dead are not conscious of anything. Yet, the Bible teaches that God can awaken the dead as if from sleep and give them life again. (Job 14:13-15) For those whom God resurrects, death is not the end of everything. - What Happens When You Die?
What Is the Resurrection?
In the Bible, the word translated as “resurrection” comes from the Greek a·naʹsta·sis, which means “raising up” or “standing up again.” A person who is resurrected is raised up from death and restored to life as the person he was before.​—1 Corinthians 15:12, 13.
Although the word “resurrection” is not in the Hebrew Scriptures, often called the Old Testament, the teaching appears there. Through the prophet Hosea, for example, God promised: “From the power of the Grave I will redeem them; from death I will recover them.”​—Hosea 13:14; Job 14:13-​15; Isaiah 26:19; Daniel 12:​2, 13.
Where will people be resurrected? Some people are resurrected to life in heaven to rule as kings with Christ. (2 Corinthians 5:1; Revelation 5:​9, 10) The Bible calls this “the first resurrection” and “the earlier resurrection,” both expressions implying that there is another resurrection to follow. (Revelation 20:6; Philippians 3:​11) This later resurrection will be to life on earth, which the vast majority of those brought back to life will enjoy.​—Psalm 37:29.
How are people resurrected? God grants Jesus the power to raise the dead. (John 11:25) Jesus will restore “all those in the memorial tombs” to life, each one with his unique identity, personality, and memories. (John 5:​28, 29) Those resurrected to heaven receive a spirit body, while those resurrected to life on earth receive a healthy physical body, completely sound.​—Isaiah 33:24; 35:​5, 6; 1 Corinthians 15:42-​44, 50.
Who will be resurrected? The Bible says that “there is going to be a resurrection of both the righteous and the unrighteous.” (Acts 24:15) The righteous include faithful people, such as Noah, Sarah, and Abraham. (Genesis 6:9; Hebrews 11:11; James 2:​21) The unrighteous include those who failed to meet God’s standards but did not have the opportunity to learn and follow them.
However, those who become so wicked that they are beyond reform will not be resurrected. When such ones die, they suffer permanent destruction with no hope of a return to life. ​— Matthew 23:33; Hebrews 10:26, 27.
When will the resurrection take place? The Bible foretold that the resurrection to heaven would take place during Christ’s presence, which began in 1914. (1 Corinthians 15:21-​23) The resurrection to life on earth will occur during the Thousand Year Reign of Jesus Christ, when the earth will be transformed into a paradise.​—Luke 23:43; Revelation 20:​6, 12, 13.
Why is belief in the resurrection reasonable? The Bible provides detailed accounts of nine resurrections, each confirmed by eyewitnesses. (1 Kings 17:17-​24; 2 Kings 4:​32-​37; 13:20, 21; Luke 7:​11-​17; 8:​40-​56; John 11:38-​44; Acts 9:​36-​42; Acts 20:​7-​12; 1 Corinthians 15:​3-6) Jesus’ resurrection of Lazarus is especially noteworthy, since Lazarus had been dead for four days and Jesus performed the miracle before a crowd of people. (John 11:39, 42) Even those who opposed Jesus could not deny the facts of the matter, so instead they plotted to kill both Jesus and Lazarus.​—John 11:47, 53; 12:​9-​11.
The Bible shows that God has both the ability and the desire to bring back the dead. He keeps in his limitless memory a detailed record of each person he will resurrect by means of his almighty power. (Job 37:23; Matthew 10:30; Luke 20:37, 38) God is able to restore the dead to life, and he wants to! Describing the coming resurrection, the Bible says of God: “You will long for the work of your hands.” ​— Job 14:15.
Who Go to Heaven?
God selects a limited number of faithful Christians who, after their death, will be resurrected to life in heaven. (1 Peter 1:​3, 4) Once they have been chosen, they must continue to maintain a Christian standard of faith and conduct in order not to be disqualified from receiving their heavenly inheritance. ​— Ephesians 5:5; Philippians 3:​12-​14.
What will those who go to heaven do there?
They will serve alongside Jesus as kings and priests for 1,000 years. (Revelation 5:​9, 10; 20:6) They will form the “new heavens,” or heavenly government, that will rule over the “new earth,” or earthly society. Those heavenly rulers will help restore mankind to the righteous conditions that God originally intended.​—Isaiah 65:17; 2 Peter 3:​13.
How many will be resurrected to heaven?
The Bible indicates that 144,000 people will be resurrected to heavenly life. (Revelation 7:4) In the vision recorded at Revelation 14:​1-3, the apostle John saw “the Lamb standing on Mount Zion, and with him 144,000.” In this vision, “the Lamb” represents the resurrected Jesus. (John 1:​29; 1 Peter 1:​19) “Mount Zion” represents the exalted position of Jesus and the 144,000 who rule with him in the heavens.​—Psalm 2:6; Hebrews 12:22.
Those “who are called and chosen” to rule with Christ in the Kingdom are referred to as a “little flock.” (Revelation 17:14; Luke 12:32) This shows that they would be relatively few in comparison with the complete number of Jesus’ sheep.​ - John 10:16.

As for your subset questions (Can the dead communicate with each other? Can the dead communicate with the living?), I will pas over it superficially.
The Scriptures are very clear that sorcerers and mediums are not allowed to exist in Israel. They are considered an abomination in the eyes of God.

31You must not turn to mediums or spiritists; do not seek them out, or you will be defiled by them. I am the LORD your God. - Leviticus 19:31
You shall not permit a sorceress to live. - Exodus 22:18
10 There shall not be found among you any one that maketh his son or his daughter to pass through the fire, or that useth divination, or an observer of times, or an enchanter, or a witch.n11 Or a charmer, or a consulter with familiar spirits, or a wizard, or a necromancer. 12 For all that do these things are an abomination unto the Lord: and because of these abominations the Lord thy God doth drive them out from before thee. - Deuteronomy 18:10-12

Mediums, magicians, and others who practice occult arts might offer entertainment by means of deception, but some mediums legitimately communicate with either the dead or with demons. The point is that any spirit not from God comes from Satan.
Saul consulted the witch of Endor (1 Samuel 28).
During the trial of Joan of Arc, she admitted that both St. Catherine and St. Margaret communicated with her.