The Byzantines followed a different form of Christianity, the branch we now call Eastern, or sometimes Greek, Orthodox. How there came to be a split between the Catholic and Orthodox traditions is complicated. You might even call it Byzantine. What matters for us are the differences between the churches, the main doctrinal one being about the dating of Easter, and the main political one being about who rules whom. Did I get my whom right there, Stan? Yes! In the West, there was a pope, and in the East, there was a patriarch.