The Greek Orthodox churches are descended from churches which the Apostles founded in the Balkans and the Middle East during the first century A.D.,[b] and they maintain many traditions practiced in the ancient Church. Orthodox Churches, unlike the Catholic Church, have no Bishopric head, such as a Pope, and hold the belief that Christ is the head of the Church. However, they are each governed by a committee of Bishops, called the Holy Synod, with one central Bishop holding the honorary title of "first among equals."
Greek Orthodox Churches are united in communion with each other, as well as with the other Orthodox Churches (such as the Russian Orthodox Church). The Orthodox hold a common doctrine and a common form of worship, and they see themselves not as separate Churches but as administrative units of one single Church. They are notable for their extensive tradition of iconography (see also: Byzantine art), for their veneration of the Mother of God and the Saints, and for their use of the Divine Liturgy on Sundays, which is a standardized worship service dating back to the fourth century A.D. in its current form. The most commonly used Divine Liturgy of the Orthodox Church was written by Saint John Chrysostom (347–407 A.D.). Others are attributed to St. Basil the Great, St. James, the Brother of God and St. Gregory the Dialogist.
The current territory of the Greek Orthodox Churches more or less covers the areas in the Balkans, Anatolia, and the Eastern Mediterranean that used to be a part of the Byzantine Empire. The majority of Greek Orthodox Christians live within Greece and elsewhere in the southern Balkans (especially in Albania), but also in Jordan, the Occupied Palestinian territories, Iraq, Syria, Lebanon, Cyprus, Anatolia, European Turkey, and the South Caucasus. In addition, due to the large Greek diaspora, there are many Greek Orthodox Christians who live in North America and Australia. Orthodox Christians in Finland, who compose about 1% of the population, are also under the jurisdiction of a Greek Orthodox Church (the Ecumenical Patriarchate).
There are also many Greek Orthodox Christians, with origins dating back to the Byzantine and Ottoman periods, who are of Arabic-speaking or mixed Greek and Arabic-speaking ancestry and live in southern Turkey, Israel, Palestine, Iraq, Syria, Lebanon, Jordan, and Egypt. They attend churches which conduct their services in Arabic, the common language of most Greek Orthodox believers in the Levant, while at the same time maintaining elements of the Byzantine Greek cultural tradition.
Ethnic Greeks in Russia and Greeks in Ukraine, as well as Pontic Greeks and Caucasus Greeks from the former Russian Transcaucasus, often consider themselves both Greek Orthodox and Russian Orthodox, which is consistent with the Orthodox faith (since Orthodoxy is the same across ethnic boundaries). Thus, they may attend services held in Old Russian and Old Church Slavonic, without this in any way undermining their Orthodox faith or distinct Greek ethnic identity. Over the centuries, these Pontic Greek-speaking Greek Orthodox communities have mixed through intermarriage in varying degrees with ethnic Russians and other Orthodox Christians from mainly Southern Russia, where most of them settled between the Middle Ages and early 19th century.