(from oca.org)
In brief, the one, undivided Church is said
to have begun on the day of Pentecost, 50 days after the
Resurrection of Christ. Already by the 4th century the term "Orthodox
Christian" was used to designate those Christians who
remained faithful to the totality of the teaching of Jesus
Christ and the apostles, as opposed to those who were known
as "heretics" who promoted false doctrines and
beliefs. [The term "orthodox" means "correct
believing" or "correct, true glory."]
Due to a variety of complex circumstances,
the Western church, known today as the "Roman Catholic
Church," split from the Eastern Orthodox Patriarchates
of Constantinople, Jerusalem, Alexandria, and Antioch in
the 11th century. Roman Catholics, however, see it from the
opposite perspective, namely that the Orthodox Church broke
communion with the Roman Catholic Church.
We Orthodox believe that we are the continuation
of the ancient Orthodox Christian Church, that we trace our
history back to Christ and the apostles, and that the Church
was "formally" established on the day of Pentecost.
The Roman Catholic Church placed itself outside of this fellowship
when it broke off communion with us in the 11th century.
This is a very brief outline; a thorough treatment
of the issue would fill volumes, and there are many resources
readily available should you wish to research the history
of this further. For more information I would recommend that
you check links on Church history. Or you may wish to read
the book by Bishop Kallistos [Timothy] Ware called "The
Orthodox Church," which gives the historical background
in detail.
For further reading:
See Church
History, section of the Fr Thomas Hopko's four-volume
work, The
Orthodox Faith
Bp Kallistos Ware's books and Fr Thomas Hopko's
books are available from booksellers and from:
St
Vladimir's Seminary Bookstore.
St.
Tikhon’s Bookstore.