Orthodox Catechism 2

What do Orthodox Christians believe about:  ?

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).

JESUS CHRIST 
is the Second Person of the Holy Trinity, eternally born of the Father. He became man, and thus He is at once fully God and fully man. His coming to earth was foretold in the Old Testament by the prophets. Because Jesus Christ is at the heart of Christianity, the Orthodox Church has given more attention to knowing Him than to anything or anyone else.
In reciting the Nicene Creed, Orthodox Christians regularly affirm the historic faith concerning Jesus as they say, "I believe... 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 heaven, and was incarnate of the Holy Spirit and the Virgin Mary, and was made man; and was crucified also for us under Pontius Pilate, and suffered and was buried; and the third day He rose again according to the Scriptures; and ascended into heaven, and sits at the right hand of the Father; and He shall come again with glory to judge the living and the dead; Whose kingdom shall have no end."

THE HOLY SPIRIT
is one of the Persons of the Holy Trinity and is one in essence with the Father. Orthodox Christians repeatedly confess, "And I believe in the Holy Spirit, the Lord, the Giver of life, Who proceeds from the Father, Who together with the Father and the Son is worshipped and glorified..." He is called the "promise of the Father" (Acts 1:4), given by Christ as a gift to the Church, to empower the Church for service to God (Acts 1:8), to place God's love in our hearts (Romans 5:5), and to impart spiritual gifts (I Corinthians 12:7-13) and virtues (Galatians 5:22, 23) for Christian life and witness. Orthodox Christians believe the biblical promise that the Holy Spirit is given through chrismation (anointing) at baptism (Acts 2:38). We are to grow in our experience of the Holy Spirit for the rest of our lives.

INCARNATION 
refers to Jesus Christ coming "in the flesh". The eternal Son of God the Father assumed to Himself a complete human nature from the Virgin Mary. He was (and is) one divine Person, fully possessing from God the Father the entirety of the divine nature, and in His coming in the flesh fully possessing a human nature from the Virgin Mary. By His Incarnation, the Son forever possesses two natures in His one Person. The Son of God, limitless in His divine nature, voluntarily and willingly accepted limitation in His humanity in which He experienced hunger, thirst, fatigue -- and ultimately, death. The Incarnation is indispensable to Christianity -- there is no Christianity without it. The Scriptures record, "...every spirit that does not confess that Jesus Christ has come in the flesh is not of God" (I John 4:3). By His Incarnation, the Son of God redeemed human nature, a redemption made accessible to all who are joined to Him in His glorified humanity.

SIN
 literally means to "miss the mark." As St. Paul writes, "All have sinned and fall short of the glory of God" (Romans 3:23). We sin when we pervert what God has given us as good, falling short of His purposes for us. Our sins separate us from God (Isaiah 59:1, 2), leaving us spiritually dead (Ephesians 2:1). To save us, the Son of God assumed our humanity, and being without sin "He condemned sin in the flesh" (Romans 8:3). In His mercy, God forgives our sins when we confess them and turn from them, giving us strength to overcome sin in our lives. "If we confess our sins, He is faithful and just to forgive our sins and to cleanse us from all unrighteousness" (I John 1:9).

SALVATION 
is the divine gift through which men and women are delivered from sin and death, united to Christ, and brought into His eternal kingdom. Those who heard St. Peter's sermon on the day of Pentecost asked what they must do to be saved. He answered, "Repent, and let every one of you be baptized in the name of Jesus Christ for the remission of sins; and you shall receive the gift of the Holy Spirit" (Acts 2:38). Salvation begins with these three steps: 1) repent, 2) be baptized, and 3) receive the gift of the Holy Spirit. To repent means to change our mind about how we have been, to turn from our sin and to commit ourselves to Christ. To be baptized means to be born again by being joined into union with Christ. And to receive the gift of the Holy Spirit means to receive the Spirit Who empowers us to enter a new life in Christ, to be nurtured in the Church, and to be conformed to God's image.
Salvation demands faith in Jesus Christ. People cannot save themselves by their own good works. Salvation is "faith working through love". It is an ongoing, life-long process. Salvation is past tense in that, through the death and Resurrection of Christ, we have been saved. It is present tense, for we are "being saved" by our active participation through faith in our union with Christ by the power of the Holy Spirit. Salvation is also future, for we must yet be saved at His glorious Second Coming.

BAPTISM 
is the way in which a person is actually united to Christ. The experience of salvation is initiated in the waters of baptism. The Apostle Paul teaches in Romans 6: 1-6 that in baptism we experience Christ's death and resurrection. In it our sins are truly forgiven and we are energized by our union with Christ to live a holy life. The Orthodox Church practices baptism by full immersion.
Currently, some consider baptism to be only an "outward sign" of belief in Christ. This innovation has no historical or biblical precedent. Others reduce it to a mere perfunctory obedience to Christ's command (cf. Matthew 28:19, 20). Still others, ignoring the Bible completely, reject baptism as a vital factor in salvation. Orthodoxy maintains that these contemporary innovations rob sincere people of the most important assurances that baptism provides -- namely that they have been united to Christ and are part of His Church.