Can somebody summarize the different "branches" of Christianity to me, and explain why they exist in the first place? All my life, I've been massively confused about how there exists separate, seemingly incompatible and separate, "branches" of Christianity. I know about "protestant", "catholic" and then there's something else in the "main three" which I probably "should know" by heart but I simply don't. And then there's also things like Mormons ("Latter Day Saints") and many other minor "variants".

I find Wikipedia and all other websites to be utterly exhausting to try to browse. They seem to always assume that you know most of what you're reading about, instead of having basically no knowledge and wanting to hear the most important elements of each "flavour" and preferably a short summary of why they are separate in the first place.

It would be much simpler if there were just "Christians", "Muslims", "Jews", etc., but it's apparently not enough to be "Christian", because all the different groups of Christians will not approve of you unless you use their "variant". At least that's how I perceive things and how they must logically be if they are different branches. I mean, why would they exist if they all agreed to the same stuff anyway?

Some (a lot, in fact) even say that Jesus was a Jew and thus Christianity in itself is branched out from Judaism? That seems like an important fact if true. It makes Christianity as a whole just some kind of "expansion pack" to the "main software product", to speak in computer jargon.

I'm really just trying to get an overview by asking this question. If such a thing can be had. I find that the more basic my questions are, the more vague are the answers.

In fact, I have never heard of any Christians who refer to the "protestant Bible" or "catholic Bible" -- it's always just "the Bible" (by which they mean the old and the new testaments combined, I assume) or "the good book" or "the holy word". Does the Bible in itself talk about and name these branches, or were they created much later, long after the Bible had been finished and spread?

I also know that the Mormons have another "testament" added to the first two, but that's just about it. And I know there's a stereotype about Catholics making a lot of children, but that also seems to be a common cliché for Mormons as well. That's just about all I know, amazingly. (It's why I ask.)
The branches come from difference in opinion. Here is a diagram showing where Christianity diverged.

Image source

From the beginning Christianity diverged from Judaism1:


  where Christianity emphasizes correct belief (or orthodoxy), focusing on the New Covenant as mediated through Jesus Christ, as recorded in the New Testament. Judaism places emphasis on correct conduct (or orthopraxy), focusing on the Mosaic covenant, as recorded in the Torah and Talmud.2


As time went on further differences in opinion let to more denominations that fell under the umbrella of Christianity.


Great Schism of 1054 was when Eastern Orthodoxy and Roman Catholicism split over3:


issues of the procession of the Holy Spirit
whether leavened or unleavened bread should be used in the Eucharist
the Bishop of Rome's claim to universal jurisdiction
the place of the See of Constantinople in relation to the Pentarchy

Reformation began around 1517-15214


had varying causes and different backgrounds by various leaders (see Martin Luther, John Calvin) caused new denominations to emerge (Lutherism, Calvinism)

Restorationism attempted to re-establish Christianity in its original form and spans over many years5


The Second Great Awakening of 1790-1840 was protestant revival movement in America that caused new denominations to emerge (Adventism, Dispensationalism, Latter-Day Saint Movement)



This is not meant to be a comprehensive list but a brief summary showing where some denominations OP mentions come from see also

1 https://en.wikipedia.org/wiki/Jewish_Christian#Split_of_early_Christianity_and_Judaism

2 https://en.wikipedia.org/wiki/Christianity_and_Judaism

3 https://en.wikipedia.org/wiki/East%E2%80%93West_Schism

4 https://en.wikipedia.org/wiki/Reformation

5 https://en.wikipedia.org/wiki/Restorationism