The Church of Rome is the primatial See of the world and one of the five Patriarchal Sees of the early Church (Rome, Constantinople, Alexandria, Antioch and Jerusalem). Founded by St. Peter in 42 AD it was consecrated by the blood of Sts. Peter and Paul during the persecution of Nero (63–67 AD). It has maintained a continual existence since then and is the source of a family of Rites in the West.
The Church of Constantinople became the political and religious center of the eastern Roman Empire after the Emperor Constantine built a new capital there (324–330) on the site of the ancient town of Byzantium. Constantinople developed its own liturgical rite from the Liturgy of St. James, in one form as modified by St. Basil, and in a more commonly used form, as modified by St. John Chrysostom.
The Byzantine Catholic Church is in full communion with the Pope of Rome. Byzantine Catholics hold the same beliefs as Roman Catholics, but often have different emphases. Byzantine Catholics have different customs and traditions that date back to the early centuries of the church.
Eastern Churches have retained a more mystical bent than Rome. A stronger tradition of monasticism and contemplative life, for example, has provided the East with a vigorous spirituality. These factors add up to a distinctive expression of faith in God. And this distinctiveness is apparent as soon as one approaches a Byzantine church. The most notable difference between a Roman Catholic sanctuary and an Eastern one is the iconostasis.
A main difference between the Eastern Orthodox and Roman Catholics has to do with the recognition of the Pope. Roman Catholics recognize the Pope as the infallible. Moreover, the Pope has supreme authority over all churches and can, for example, contradict or usurp the power of a lower ranking church leader (e.g., a priest, bishop or cardinal).
For Roman Catholics, Holy Matrimony is a binding, ostensibly an unbreakable, contract. The man and the woman marry each other with the "church" (bishop or priest) standing as a witness to it. Hence, no divorce under any conditions - no divorce but annulment of the marriage contract if some canonical defect in it may be found which renders it null and void.
In Orthodoxy, Holy Matrimony is not a contract; it is the mysterious or mystical union of a man and woman - in imitation of Christ and the Church - in the presence of "the whole People of God" through her bishop or his presbyter. Divorce is likewise forbidden, but, as a concession to human weakness, it is allowed for adultery. Second and third marriages are permitted - not as a legal matter - out of mercy, a further concession to human weakness.