The Orthodox Church was founded by our Lord Jesus Christ and is the living manifestation of His presence in the history of mankind. The most conspicuous characteristics of Orthodoxy are its rich liturgical life and its faithfulness to the apostolic tradition. It is believed by Orthodox Christians that their Church has preserved the tradition and continuity of the ancient Church in its fullness. Today the Orthodox Church numbers approximately 300 million Christians who follow the faith and practices that were defined by the first seven ecumenical councils. The word orthodox ("right belief and right glory") has traditionally been used, in the Greek-speaking Christian world, to designate communities, or individuals, who preserved the true faith (as defined by those councils), as opposed to those who were declared heretical. The official designation of the church in its liturgical and canonical texts is "the Orthodox Catholic Church" (gr. catholicos = universal).

The Orthodox Church is a family of "autocephalous" (self governing) churches, with the Ecumenical Patriarch of Constantinople holding titular or honorary primacy as primus inter pares (the first among equals). The Orthodox Church is not a centralized organization headed by a pontiff. The unity of the Church is rather manifested in common faith and communion in the sacraments and no one but Christ himself is the real head of the Church.

In the wider theological sense "Orthodoxy is not merely a type of purely earthly organization which is headed by patriarchs, bishops and priests who hold the ministry in the Church which officially is called "Orthodox." Orthodoxy is the mystical "Body of Christ," the Head of which is Christ Himself (see Eph. 1:22-23 and Col. 1:18, 24 et seq.), and its composition includes not only priests but all who truly believe in Christ, who have entered into the Church He founded, those living upon the earth and those who have died in the Faith and in piety."