What is Orthodoxy?

WHAT IS THE ORTHODOX CHURCH?
Orthodox Christians affirm that their Church is the living continuation of the Apostolic Church, founded by Christ himself; they believe that it has maintained, without distorting addition or damaging detraction, the ancient faith of the undivided Church. The Orthodox make these claims in all humility, readily admitting the shortcomings of their Christian witness. They have no intention of calling into question the sincerity and integrity of other Christians. But they do assert that "if a person carefully examines the history of Christianity, he or she will soon discover that the Orthodox Church alone is in complete sacramental, doctrinal, and canonical continuity with the ancient undivided Church as it authoritatively expressed itself in the great Ecumenical Councils."
GREEK, RUSSIAN, OR WHAT?
You may have heard of the Greek Orthodox Church and the Russian Orthodox Church, and perhaps some other Orthodox Churches such as the Antiochian, the Serbian, the Romanian, etc. Are they different Churches? No, they are all Orthodox Churches. The national name associated represents the country where they are established, just as "Presbyterian, USA" identifies a Presbyterian Church in the United States, as opposed to its sister Churches in Scotland and England.
But then, why are all these Orthodox Churches in America? The answer is that whenever Greeks or Russians or Serbs or Romanians immigrated to America they brought their own Church with them, just as the Scots brought their Calvinist Presbyterian Church, the Germans their Calvinist Reformed Church, and the Dutch their Calvinist Dutch Reformed Church. The same thing happened with the Lutherans - until recently there were Lutheran Churches in America that thought of themselves (in addition to being American) as Swedish, Danish, or German. And, just as it took over a hundred years for most of the Lutherans to become one Evangelical Lutheran Church in America, the process of uniting the Orthodox Churches in America is a slow process, but one that is gradually occurring.
The various Orthodox Churches are all sister Churches, all part of the One, Holy, Orthodox Catholic Church. Members of one are recognized as fellow Orthodox by the others, and welcome to receive the sacraments at the other Orthodox Churches and to become members of whatever Orthodox Church is convenient for them. Most Orthodox churches in America now have as members people of all ethnic backgrounds, including many converts, regardless of what "nationality" the parish has in its title.

What we believe:
The Nicene CreedThe Symbol of Faith of Orthodox Christians
I believe in one God, the Father Almighty, Maker of heaven and earth, and of all things visible and invisible: And in one Lord Jesus Christ, the Son of God, the Only-begotten, Begotten of the Father before all ages, Light of Light, True God of True God, Begotten, not made; of one essence with the Father, by whom all things were made: Who for us men and for our salvation came down from the heavens, and was incarnate of the Holy Spirit and the Virgin Mary, and became man; And was crucified for us under Pontius Pilate, and suffered and was buried; And rose again on the third day, according to the Scriptures; And ascended into the heavens, and sitteth at the right hand of the Father; And shall come again, with glory, to judge both the living and the dead, Whose kingdom shall have no end. And in the Holy Spirit, the Lord, the Giver of Life, Who proceedeth from the Father, Who with the Father and the Son together is worshiped and glorified, Who spake by the Prophets; In One Holy Catholic and Apostolic Church. I Confess one Baptism for the remission of sins. I look for the Resurrection of the dead, And the life of the age to come, Amen.