This refers to the orthodox churches and those sharing the spiritual and cultural ethos which derives from the Byzantine Empire. There are over 214 million Orthodox Christians today. The churches extend across Eastern Europe, Slav countries and the eastern Mediterranean. The split with the western church came about because of conflict over the Pope's claim to supreme authority and a clause added to the church's creed which said that the Holy Spirit came from the Son of God as well as God.
Veneration of icons is an important part of public and private worship.
Monastries have played an important part in the history of the church. Mount Athos in Greece has been the chief monastic centre since the 10th century. It is the largest of the Christian denominations, with approaching a billion members. It's origins are from the Western church of the Middle Ages. When defining matters of faith or morals what the Pope says is regarded as infallible and binding on all Catholics.