I think to answer your question, you simply have to do a little research on the history of Christianity. I'll give ya the "nutshell" version, but
you may want to look up the details for yourself.
The word, "catholic" in its original Greek and Latin (long before the Christians were established) meant "world wide" or "universal." It's
still used in that way today by scholars who write long and dull papers;
So when it was founded, it was the "Universal Christian Church -- accept no substitutes."
Christianity was a real mish-mash in those days. If you think Protestantism has a zillion little cult churches, well, early Christianity had this all
beat. Because there wasn't any "official doctrine book", each Christian church had a different set of books and letters and so forth that it used
as guidelines for how worship was supposed to go and bishops of different cities would quarrel with local churches and each other about who was
Around 300 AD the whole thing was so divisive and such a mess that a huge convention of bishops and popes and the like was called to come up with ONE
book and ONE set of principles they could agree on. It took them over 100 years.
Out of this comes the Bible (which was not a universally agreed on set of books... there were a number of very popular scriptures that were put into
an "appendix". A scholar bishop named Jerome (St. Jerome) worked on the books, translating them out of a real mishmash of languages (including some
that weren't terribly literate) and trying to edit them into one coherent book.
That's the Vulgate Bible in Latin.
They come up with a creed (the Apostle's Creed (this is a good page on it) and other things that represented what the Christian faith stood for:
Big fights continued over doctrine points (including whether there was a trinity or not) -- too long to go into here, but you can look up things like
the Aryian heresy.
I'm going to one-line this and say "in the 10th century or so the church split into the Greek Orthodox Catholic Church and the Roma Catholic
Church." There's a very long and very fascinating story behind this, involving the sacking of Rome, the position of Roman emeprors as the High
Priest of the god/gods, cowards, heroes, idiots, the Dark Ages and the preservation of knowledge in the East by the Greek Orthodoxes... but you'll
have to look it up.
It's fascinating. Really.
The two churches continue (reforming corruption on occasion, torching the occasional heretic, etc, etc) until the rise of Protestantism.
Protestantism does away with the extra-canonical books and develops into a mess with Protestants taking only the things that the liked from the
Catholic Church as their theology (so some sects have saints but most don't. This is also where the notion that "babies and the innocent go to
heaven" -- an offshooot of the Catholic belief which was a reaction to the treatment of babies in the Bible (children not "of the faith" went to
hell) comes from.
Protestant churches originally had ruling bodies (synods) similar to the Catholic church, but without a pope. The leaders were elected -- however,
anyone who disagreed could go start their own branch of Christianity. So the Anglicans and Lutherans aren't too far away from the Catholic beliefs
and so forth, but the churches like "Potter's Wheel" are... somewhere off the map:
The Catholic churches don't actually have different teachings. They teach what is dictated by the governing body, though each one may emphasize
different things or have different types of services to meet the needs of the community. Roman Catholic practices and beliefs are slightly different
from Greek Orthodox... if I had to guess I'd sat that Greek Orthodox Catholics are slightly more similar to the teachings of the first Christian
churches, but that's a non-researched guess.
As time went on, more teachings that weren't in the original churches develop (including the "end times theology")