Fr John Flader: Catholc, Orthodox…what’s the difference?

I have friends who belong to various Eastern Rites and others who are Orthodox. Sometimes I get confused about which is which and how they relate to the Catholic Church. Could you please give me a little background on this to make it clearer?

Perhaps it would be easiest to begin with the Orthodox Churches and how they came to be separated from the Catholic Church.
There are two main groups of what we now call “Orthodox” Churches. The first group, which is smaller, separated from communion with the Catholic Church in the fifth century, following two ecumenical councils.
In 431 the Council of Ephesus proclaimed that Jesus Christ was one person, the divine person of the Word, and it condemned the errors of Nestorius, who taught that there were two persons, a divine one and a human one.
After the Council some followers of Nestorius left the Church and eventually became what is now the Assyrian Church of the East. That Church no longer holds the Nestorian heresy.
Twenty years later, in 451 the Council of Chalcedon proclaimed that in Christ there were two natures, the divine and the human, and it condemned the errors of Eutyches who maintained that there was only one nature, an error known as “monophysitism”. Today there are five Churches that separated after the Council of Chalcedon: the Armenian Apostolic, Coptic Orthodox, Ethiopian Orthodox, Syrian Orthodox, and Malankara Orthodox Syrian Churches. These five Churches are in communion with each other.
The largest group of Orthodox Churches comprises those that separated from Rome in 1054, when the papal representative Cardinal Humberto da Silva excommunicated the Patriarch of Constantinople Michael Cerularius, and the Patriarch in turn excommunicated the papal legates then in Constantinople.
Following the excommunications, the four Patriarchates of the East and the Church in the countries that had been evangelised by missionaries from the East separated from Rome and went into schism, no longer recognising the authority of the Pope. Naturally there were more fundamental issues than the excommunication itself that brought about the lasting split, which is today known as the “Great Schism”.
The principal present-day Orthodox Churches that broke away in 1054 are the Patriarchates of Constantinople, Alexandria, Antioch and Jerusalem, and the Orthodox Churches of Russia, Serbia, Romania, Bulgaria, Georgia, Cyprus, Greece, Poland, Albania, Czech and Slovak Republics and the Orthodox Church in America.
In addition, there are other Churches that depend on the ones just mentioned.
These Churches accept the teachings of the first seven ecumenical councils and they have valid sacraments, including the priesthood. Their faithful are allowed to receive the sacraments of the Eucharist, Reconciliation and the Anointing of the Sick from a Catholic priest.
Over the centuries following 1054, some parts of these Orthodox Churches returned to full communion with Rome and were for that reason sometimes called “Uniate” Churches.
They are referred to more properly as Catholic Eastern Churches and they retain their Eastern liturgical and disciplinary traditions.
They are governed by the Code of Canons of the Eastern Churches, promulgated by Pope John Paul II in 1990 and by their own particular laws.
They are the Coptic, Ethiopian, Syrian, Syro-Malankara, Armenian, Chaldean, Syro-Malabar, Byelorussian, Bulgarian, Greek, Hungarian, Italo-Albanian, Melkite, Romanian, Ruthenian, Slovak, Ukrainian, Yugoslavian, Albanian and Russian Churches.
In addition to these 20, there is the Maronite Church, which has always been in union with Rome.
It is these Catholic Eastern Churches that are often referred to as Eastern Rite Churches.
They are fully part of the Catholic Church and contribute greatly to the universality and richness of the Church by their diverse traditions.
A fuller treatment of this subject can be found in Archbishop Michael Sheehan’s Apologetics and Catholic Doctrine, edited by Fr Peter Joseph.