Holy Trinity
Most Christians believe that God is one eternal being who exists as three separate, eternal, indivisible persons (or more correctly called "persons"): the Father, the Son, and the Holy Spirit.
From Judaism comes the belief that there is one Almighty God who is the Creator of the Universe and maintains its existence. Against this background, belief in the divinity of Christ and in the divinity of the Holy Spirit is expressed in the doctrine of God's trinity (in Western theological thought) or in the Holy Trinity (in Eastern theological thought). According to this doctrine, three persons (hypostases) have one divine nature. This nature is not separate, but rather each person has this divine nature. The differences consist only in origin (not in a temporal sense) and the relationship between persons - the Father is unbegotten, the Son is eternally begotten of the Father, the Spirit is eternally proceeding from the Father. The very property of God's existence is His existence as the Holy Trinity. The Trinity of God must be perceived at different levels of His unity.
The word "begotten" does not refer to the birth of Jesus from Mary, but to the eternal and divine "birth" before creation. God the Son existed eternally before becoming human and becoming incarnate. During the Aryan dispute, the orthodox formulation was that “there was no time when the Son did not exist.”
Most Christians believe that salvation from “sin and death” is available through faith in Jesus as Savior through His atoning sacrifice on the cross where He “atones” for our sins. Acceptance of salvation is associated with justification and is usually understood as the operation of God's grace.
Images of the impact of God's grace are understood differently in different traditions. Catholicism and Eastern Orthodoxy teach the necessity of interaction between human free will and the grace of God. Reformed theology (most notably the teaching of Calvin) goes even further, emphasizing man's dependence on grace, as it teaches about the complete sinfulness of mankind and irresistible grace. In the Arminian teaching, the leading role is played by the independent nature of freedom of choice (salvation), the original grace of faith and the dependence of salvation on God’s grace is given to all people. The differences here underlie different views on the traditions of understanding original sin. (See articles about each individual historical movement)