Well... Christians started off as one Church. They were the only holy Catholic and apostolic Church which believed in the Orthodox faith.
The Christians around modern Egypt got upset at a Church Council over things that really didn't matter to anyone even in the fifth Century. They were mere differences in understanding and language that with more patience and understanding, we find can be easily resolved today. So, they stopped showing up to Ecumenical Councils.
The rest (but not all) of most of Christianity was divided between two groups, the Latins, and the Greeks. They were divided by language (theologically), culture, and practice. The two sides became politically isolated. The Latins lived in the Western Roman Empire, which collapsed, was taken over by barbarian tribes, and those tribal leaders converted to Christianity. So the Pope, the Bishop of Rome, considered the leader of the Latins and the leader of the Church, whose power was never defined, recognized these now kings as legitimate rulers of the former western part of the Roman Empire.
The Greeks, who controlled the Roman Empire, which was not Latin or Roman... were not happy that their Latin brothers gave up on the Empire, which had become Christian. The Pope made the King of the Franks, now France and much of Germany, an Emperor. The Greeks were not thrilled, since they had the Emperor. Then a bunch of German and Italian regions got together in an overly complicated political entity that only Germans and Italians could create, called the Holy Roman Empire. You know, as opposed to just the Roman Empire (which the Greeks were).
Then the two sides stopped getting together and really haven't done anything since. So that Latins called themselves Catholic, after the Church... and the Greeks, Orthodox, after the faith.
So this is in the 1000s. In the 1500s, the Italians left the Holy Roman Empire. But the princes of Germany were not happy about how much money still ended up in Rome because of the Church. So, a guy, who became a monk, because he told God he'd become one if he survived a storm, had legendary bowel movement issues. He took his rage out on the Church.. and the Jews... and shopped around the princes of Germany for people interested in excuses to leave the Church. Also, he told them they could close down monasteries and sell all their land.
There was no "Germany" at this time. Just a bunch of little duchies with their own rulers. His gimmick was, you can control your land and your church, by leaving the church, in the name of reforming the Church. Control religion and your kingdom, for the good of Christianity!
Meanwhile, in England, Henry VIII wanted to marry his dead brother's wife. The Church is like... no... you can't marry your brother's wife... read the bible. But Henry says... technically, they weren't married, since they didn't have relations. His wife, a devout Christian and loved figure confirmed it was true, he was sick after their married and then died.
So the Church says alright, you can get married. So he tries to make lots of kids, sometimes with his actual wife. He has five legitimate kids, but four of them died, leaving him only a girl and a wife probably too old to have more kids. England didn't really have plans for a Queen as a ruler, as opposed to a Queen-consort. So Henry VIII tells Rome, I changed my mind, I am married to my brother's wife. Let's say the marriage never happened because it couldn't. Rome is like... no.
So Henry VIII decides to leave the Catholic Church while pretending to be part of the Catholic Church. He married five more times and kills lots and lots of people, including his most trusted friend Thomas Moore, who would not recognize Henry as the head of England and the head of the Catholic Church in England. Ironically, the daughter of his first wife became Queen anyways. Her name was Mary and hundreds of people died with her trying to return England to Catholicism. Then his second wife, which was adultery, gave him a daughter, named Elizabeth. She also became Queen and killed thousands of Catholics, gotta out do your sister, returning England to pretend Catholic.
Meanwhile, a Christian has tried to improve Christianity by interpreting it with Islamic philosophy. If you have ever read the Quran, you know it makes no sense. So, they decided, God can't be understoodd, and He does whatever He wants. God is in control of everything.
So Calvin decided, for God to be really in control of everything, then God picks people to go to hell and go to Heaven, for his glory, apparently. He makes long rationalizations for this idea. So now you have the folks who leave the Catholic Church while pretending to be Catholics (Lutherans, Anglicans), and the folks that hate everything Catholic (Calvinists/Reformed).
In England, people don't like what happened with the Catholics and the pseudo-Catholics. They think if they get rid of all things Catholic and embrace Calvinism, everything will be fine. So Elizabeth, the second queen daughter from the guy who wanted a son, says.. let's compromise on Christianity. And she mixes a bit of this and a bit of that. And I'll kill anyone that disagrees.
In Germany, the folks that didn't like Catholicism and didn't like Lutherans, and all the bloodshed and violence decided to start their own faction call Anabaptists.
And it didn't go well, at all. Eventually we decided you should believe whatever you want. That is, you can believe what you want... but I'll find ways to force my beliefs on your subtly. (We use the terms "faith" and "values" in political commercials to let you know)
Then many Christians forgot Christian history and theology. That's a lot of stuff. So, we should just focus on the bible. But everyone's interpretation of the bible creates another denomination. So then we decided to unite ourselves by completely dividing ourselves while holding onto factional theologies. Because, that is apparently biblical... if you completely ignore history.
In short, the Coptic, Orthodox, and Catholic Churches are a continuation of Christianity separated by time and circumstance. The rest are organizations made by men and women.