Mormonism is the theology and religious tradition of the Latter Day Saint movement of Restorationist Christianity started by Joseph Smith in Western New York in the 1820s and 1830s. As a label, Mormonism has been applied to various aspects of the Latter Day Saint movement, although since 2018 there has been a push from The Church of Jesus Christ of Latter-day Saints (LDS Church) to distance itself from this label.
A prominent feature of Mormon theology is the Book of Mormon, a 19th-century text which describes itself as a chronicle of early Indigenous peoples of the Americas and their dealings with God. Mormon theology includes mainstream Christian beliefs with modifications stemming from belief in revelations to Smith and other religious leaders. This includes the use of and belief in the Bible and other religious texts, including the Doctrine and Covenants and the Pearl of Great Price. Mormonism includes significant doctrines of eternal marriage, eternal progression, baptism for the dead, sexual purity, health, fasting, Sabbath observance, and formerly, plural marriage.