Members of The Church of Jesus Christ of Latter-day Saints believe that the fullness of the gospel of Jesus Christ, and the divine priesthood authority to act in His name was lost from the earth through an apostacy, which then needed to be restored. This Restoration happened in 1820 through a latter-day prophet chosen by Jesus Christ, named Joseph Smith.
To Learn More
1. Mormons & Jesus Christ: jesuschrist.lds.org
2. About the Prophet Joseph Smith: josephsmith.net
3. About Mormon beliefs: Mormon.org