Which groups were divided during the Great Schism?

The Great Schism refers to the permanent separation of the Eastern and Western Christian Church in 1054 AD. As Christianity spread across Europe, it developed some regional differences, especially related to theology (e.g. disputes about the Trinity) and church practice (e.g. what type of bread should be used in the Lord's Supper). Additionally, there was tension among the centers of Christianity (particularly Rome in the West and Constantinople in the East) about whether one of them should have primacy over the others, and if so, which one. Rome believed it should possess universal jurisdiction since it had been founded by Peter, and Christ had said that he would build his rock upon Peter (according to the Roman Catholic interpretation); Constantinople did not. All of these tensions were heightened by the great distance between the East and West.

Eventually, these disputes--among others--bubbled over into permanent separation. Since 1054, the Roman Catholic Church and the Eastern Orthodox Church have been permanently separated and have developed mostly independent of one another. Eventually, the Protestant Church broke off from the Roman Catholic Church, leaving Christianity with three main branches.