Religion question (churches) roman catholic vs. christian?

Actually, Catholicism is NOT a denomination. A denomination is a religious group that was founded by people. Catholicism was founded by Jesus Himself, so it is not a denomination. Also, in everyday speech, "denomination" is usually used to mean a Protestant group. To answer your question, I suggest you read a book called "Where We Got The Bible", so sorry I can't remember the author! It's rather a detailed question to answer here.