Mormon theology is the beliefs of a number of Christian groups, especially the Church of Jesus Christ of Latter-Day Saints (LDS Church), but also includes a few other splinter groups that identify as Mormons. While Mormon theology shares many beliefs in common with mainstream Christian theology, it differs in several key ways. Most notably, Mormons accept the Book of Mormon and some other documents as Scripture, they reject the doctrine of the Trinity, and they have different beliefs regarding the afterlife.
Most Mormons belong to the LDS Church, which follows the teachings of its founder, Joseph Smith, and an ongoing succession of prophets. Mormons believe that Smith received the Book of Mormon as a revelation from God. The Book of Mormon teaches that mainstream Christians were part of a great apostasy, in which truths about God and God's will were lost. They believe the "Restored Gospel" of Mormonism to be the corrected and expanded form of correct Christian doctrine. The Book of Mormon and the Doctrine and Covenants as well as the Old and New Testaments are all considered Scripture in the LDS Church.
According to Mormon theology, both God and Jesus have physical bodies, but the Holy Ghost does not. This differs from the view of the Trinity held by most other Christian groups, in that the Father, Son and Holy Ghost are described as three separate beings, rather than three beings in one. God is believed to be the literal, physical father of Jesus, and the "spirit father" of all humankind.
Like most other Christians, Mormons believe that people can be saved from their sins through Jesus Christ. According to Mormon theology, however, salvation is the result of good works, such as baptism and following the teachings of the church, rather than solely by grace. A person who is saved through Jesus will, after death, go to one of three heavenly kingdoms.
The Celestial Kingdom is the highest of these and is reserved for those who followed the ordinances and covenants of the church during their lifetime, or who have had someone else perform ordinances for them by proxy after death. In this state of "exultation," a person has a physical body, remains united with his or her family, and has the opportunity to become the god of his or her own planet. The other two kingdoms, the terrestrial and the telestial, contain those who are saved, but not "exalted." Some, called the "sons of perdition," are sent to the "outer darkness."
Other groups who also call themselves Mormon, but who are not part of the LDS Church, may have slightly different theological views. Fundamentalist Mormons, for instance, believe that polygamy, or "plural marriage" is essential in order to enter the Celestial Kingdom. The LDS Church, however, did away with the practice of polygamy in 1890.