Well, hopefully without sparking a big fight, Christianity is not just a bunch of people trying to figure out the scriptures which fell out of the sky.
The Roman Catholic Church actually has it's roots in Jerusalem before the Jewish war in 66ad. Before this time, Jewish Christians lived in relative communion with Jews. However, after this failed revolt, the Christians retreated to Pella (A city across the Jordan) After the commotion settled, The Christians (needless to say) were no longer welcome in what was left of Jerusalem.
Eventually, (within the next 10 years or so) Christianity found it's home in Rome. Initial fierce persecutions continued until about 311AD when Constantine came into power. With the new freedom from persecution, the church grew and became more integrated with Roman civilization. This opened the door to many modes of heretical thought. Namely Gnosticism, Pelagianism, Donatism, and the ever popular Arianism. At any rate, mot of these modes of thought were based upon incorrect suppositions of the natures of God the Father, Jesus, and the Holy Spirit. Mind you that all this time, though the Gospels have been written (along with countless other writings, there is no defined canon of scripture(no Bible). However, the councils of Nicea, Constantinople, and Chalcedon eventually develop the understanding of the trinity and put the early heresies to bed. Additionally in that time period, at the synods of Hippo, and Carthage (393-397AD), the scriptural canon were set forth (with much debate). So nowaround the year 500, the church is doing ok and scripture is set, and Rome Falls! Uh oh....
Well the invading germanic tribes (Goths, Franks, Algles, and Saxons to name a few) are layin' the smack down on what's left of the Roman armies. However, the Germanic peoples were largely pagan in belief (except the Goths who were Arian) and tribal in civilization. The winning of the roman territory resulted in a situation which was alot like trying to play checkers on a chess board with chess pieces.
Naturally, the socially infused church was looked to for governance which blurred the line between church and state and led to much curruption in the church at this time and for centuries to come. The tribal nature of the invaders led to a splitting up of the roman territories. In the centuries to come, this would come to lead to feudalism...
Well, a few more centuries later, a man named Mohammed is born to a middle eastern merchant. Convinced that he is a prophet, he brings his prophecy to the church where it is rejected on many accounts. Needless to say, he wasn't too happy. He goes off and starts his own religion which is now called Islam (I guess you could call him the first protestant)

. ok, bad Joke, sorry... At any rate, Mohammed and his followers grew quickly in North Africa where Donatism was still floundering. At any rate, Islam spread like lice through a Wig Shop (That's mine but you can use it) and soon began taking Christian territory by force. Enter the infamous "crusades". (No, Billy Graham didn't lead this charge) The crusades were originally a Church led recapture of the Holy land from the Muslims and later, after initial success there would be six more which would eventually prove to be unjustly motivated (at least partially) and one (the fourth) resulted in the sack and pillage of Constantinople (the seat of the eastern church) and the establishment of a latin (Western) heirarchy there. This offence would prove later to be instrumental in the separation of the "Eastern Orthodoxies" from the Roman Catholic Church. There would eventually be six official Crusades in all not counting a tragic "children's crusade" in the year 1212.
Moving on, in the centuries to come, the Church would come to withstand more schism, corruption, and still manage to found the first "universities" which would later develop into whay we know know as higher education. As well, the moral guidance of the church kept the lid on feudalism (to some extent). Now we skip ahead a few hundred more years to the protestant reformation.
Now mind you, up until now, the church has had it's tyrants and saints. The clergy in certain parts of the world are certainly currupt and doing many things which were not in keeping with church teaching. However, through it all, the church has been faithful to Christ's prayer in Jn 17:20-21
20 "I pray not only for them, but also for those who will believe in me through their word,
21 so that they may all be one, as you, Father, are in me and I in you, that they also may be in us, that the world may believe that you sent me. (Emphasis added)
and the Apostle Paul's admonition in 1 Cor 1:10,12-13 about the church's oneness.
10 Now I beseech you, brethren, by the name of our Lord Jesus Christ, that you all speak the same thing and that there be no schisms among you: but that you be perfect in the same mind and in the same judgment
12 Now this I say, that every one of you saith: I indeed am of Paul; and I am of Apollo; and I of Cephas; and I of Christ.
13 Is Christ divided? Was Paul then crucified for you? Or were you baptized in the name of Paul?
However, Along comes Luther who is utterly discusted with the abuses in the church in his time and place (and rightfully so). However, Luther does something unthinkable. Luther departs from the Church and effectively starts his own. To support this "move" he asserts that the sacred writings of Scripture are Authoritative apart from the authority of the universal church. Ironically, he then (almost immediately) alters the canon of scripture and re-words certain passages to suit his doctrines. Seems to fly in the face of what he preached.
Needless to say, this new "group" of believers were originally called the "protesters" by the church. Time for a council? I'd say it's high time!. Enter the Council of Trent. With this council, many abuses were put down but many of Luther's other Theses were to be denied. Needless to say, Luther was not pleased. In fact, his contempt for the church is quite evident in most of his writings (to say he least). At any rate, from this point on, Luther and his followers were dubbed protestants (in that they were protesting their Catholic faith). However, almost immediately, there sprung up dissent in the Luther camp. People disagreed! (Imagine that) But unlike the Catholic faith of the last 1500 years, there was no auhority in protestantism to call a council and discuss matters. So, people took their bibles and went home.... such is still the practice today. Within protestantism, if you don't agree with someone, you don't have to work it out and come to an understanding (even if it's begrudgingly) you can just go start your own church.
The splintering of protestantism is really too numerous to count. I've heard estimates based upon clerical registrations for business licences to be around 30,000 distinct denominations or more, but I haven't been able to substantiate this claim.
At any rate, I've left out a great deal of information (needless to say) some good and some bad for both parties. However, what I have stated is accurate to the best of my knowledge.
In closing, little resemblance can be found today in the churches that remain from the original reformer Luther. For instance, Luther displayed a considerable honor of the virgin Mary, and many other doctrines which his "followers" have since abandoned.
Additionally, the Catholic church continued after the departure of the "protestants" and later the church of England under King Henry VIII. It "cleaned up it's act" so to speak though as always there remain some of the blemishes of scandal. However, as a Catholic myself, the element of human weakness and sin which has always been an unfortunate part of the church, just demonstrates the fact that
that the churchs remarkable resilience is not at all due to the cunning or strength of certain men and women, but to the unfailing guidance and providence of the Holy Spirit. Esentially, Christ meant what he said when he promised that
"the gates of the netherworld shall not prevail against it". And when He said:
"behold I am with you all days, even to the consummation of the world