system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What are the main differences between Roman Catholicism, Protestantism and Orthodoxy?
gpt
As the church got more organized differences in how churches were organized and how they practiced the rituals of their faith grew. Eventually these differences grew large enough that a church split, in church history the most important splits are called schisms.  

The first major schism occurred between the now Orthodox and now Catholic churches and involved the major issue of would Rome be sole head of the faith or would each nation have its own head of the faith.  The Catholic church follows Rome, while the Orthodox churches have national heads.  

The next major schism occurred after Gutenberg greatly reduced the cost of printing books.  Prior to then, only the church and very wealthy individuals could afford to pay people to hand copy books (so the church was the only interpreter of the bible because they were nearly the only owners of bibles).  As a result of cheap books, a difference grew between soon to be Protestants who preferred decentralized interpretation of the bible (right down to individual believers owning a copy of the bible and reading and interpreting it themselves) and Catholics who prefer a single interpretation of the bible.  While the seeds were planted by the printing press, Protestantism got started when Martin Luther nailed 95 theses (or protests) of Church practices to a church door (hence the name Protestants).