As the Apostolic Creed states, “We believe in one God: God the Father the Pantocrator (Almighty) who created Heaven and earth and all things seen and unseen;
We believe in one Lord Jesus Christ, 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 and for our salvation came down from heaven and was incarnate of the Holy Spirit and of the Virgin Mary and became man; and He was crucified for us under Pontius Pilate, suffered and was buried; and on the third day He arose from the dead according to the Scriptures, ascended into the heavens, sat at the right hand of the Father, and He shall come again in His glory to judge the living and the dead, of whose kingdom shall be no end.
Yes, we believe in the Holy Spirit, the Life-Giver, who proceeds from the Father, Who with the Father and Son is worshipped and glorified. And in one holy, catholic and apostolic Church, we look for the resurrection of the dead and the life of the world to come. Amen.
Thus, the Orthodox Church believes in the Holy Trinity, that the three are One.
The Christian Church is based on the life and teachings of Jesus Christ, the eternal Son of God, Who came into the world as a man. This is the foundational belief of every Christian.
— An Introduction to the Orthodox Conception of the Holy Trinity