What form of organized Christianity existed in Europe before Catholicism, and how did it differ from early Catholicism? How did Catholicism then become the dominant Christian denomination in Europe?

by Pandamage

I've never really been taught much about what happens between the adoption of Christianity by the Romans and the majority of Europeans following the catholic faith. So what forms of organized Christianity existed before then?

chilaxinman

Are you asking for a rundown of the history of Christianity? That's cool if you are, but I just want to make sure I know what you are looking for.