Through these revelations, Mormons believe that God our Heavenly Father, Jesus Christ, and the Holy Ghost are three distinct personages with separate roles but who are, nevertheless, united in purpose. Heavenly Father and Jesus Christ have glorified bodies of flesh and bones while the Holy Ghost is a Spirit.
Mormons believe that all men and women are literal spiritual children of God, that we lived with Him before we came to Earth, and that we can return to live with Him. During the premortal life with God, He prepared a plan (often referred to as the Plan of Salvation) through which His children can return to live with Him and enjoy all of the blessings of immortality and eternal life. Perhaps the greatest blessing of eternal life is that through the atonement of Jesus Christ, we can be with our earthly families forever.
Central to Mormon theology is the fact that Jesus Christ is the literal Son of God who came to Earth to perform the atonement, which includes Christ's suffering in Gethsemane and on the cross of Calvary, and His triumphal resurrection. Mormons believe that there is no way for Mankind to receive salvation other than through Jesus Christ. Through the atonement, every person who has been born will be resurrected, and everyone can be cleansed from sin. All other doctrines are ancillary to the doctrine of the Atonement of Jesus Christ.
Good works, including ordinances, are also an essential part of Mormon theology. Without works, Mankind cannot have access to the blessings of the Atonement of Jesus Christ because, even though He wishes to save all His children, God cannot save us unless we let Him (see Agency). Moreover, the ordinances which allow us to access the blessings of Jesus' atonement must be performed by men who hold the Priesthood. The Priesthood is the authority to act in the name of God.
To learn more about what Mormons believe, visit www.mormon.org.