What's the difference between the catholicism and orthodox churches?

beside the pope.. I want to know the doctrines and traditions for e.g do orthodox celebrate novenas or devotions to saints like catholics do? do they have same saints? I know they don't have the same saints but they must have at least the same saints until the separation? why do orthodox churches don't let catholics to take the communion? if both churches are almost the same.. both recognize the creed of nicea and stuff like that no? please compare them and differences.. thank u