he Eastern Catholic Churches Churches are churches that follow the ancient liturgical traditions of the East, while being in full communion with the Roman Catholic Church and placing themselves under the authority of the Bishop of Rome.
Some of these churches, like the Orthodox Churches, follow the Byzantine tradition, while others follow other liturgical traditions. The history of each Eastern Rite Catholic church is unique, some having sided with Rome at the time of the Great Schism and some being joined to Rome after that time.
They are sometimes referred to as Uniates, a term which many Eastern Catholics reject as derogatory, although it was historically used by both Eastern Catholics and the Latin hierarchy, as well.
Many of these churches have a direct non-Catholic (usually Orthodox or Oriental) counterpart. Others exist only within the Catholic Communion as they were either entirely received into communion with the Roman See or never left that communion. (OrthodoxWiki)