The Orthodox Church believes in one God, almighty; God the
Father, God the Son, and God the Holy Spirit.  The one God of
Orthodoxy is a Triune God, triune meaning “three, yet one”.  
God the Father is the fountainhead of the Holy Trinity. The
Scriptures reveal the one God is Three Persons -- Father, Son,
and Holy Spirit -- eternally sharing the one divine nature. From
the Father the Son is begotten before all ages and all time
(Psalm 2:7; II Corinthians 11:31). It is from the Father that the
Holy Spirit eternally proceeds (John 15:26). God the Father
created all things through the Son, in the Holy Spirit (Genesis 1
and 2; John 1:3; Job 33:4), and we are called to worship Him
(John 4: 23). The Father loves us and sent His Son to give us
everlasting life (John 3:16).
In Orthodox terminology the Father, the Son and the Holy Spirit are called three divine
persons. Person is defined here simply as the subject of existence and life. In this view, the
Son and the Spirit are both one with God and in no way separated from Him. Thus, the Divine
Unity consists of the Father, with His Son and His Spirit distinct from Himself and yet
perfectly united together in Him.
What Orthodox Christians Believe