The Latter Day Saint movement (also called the LDS movement or LDS restorationist movement) is a group of independent churches tracing their origin to a Christian primitivist movement founded by Joseph Smith, Jr. in the late 1820s. Collectively, these churches have over 14 million members. The vast majority of them are Mormons belonging to The Church of Jesus Christ of Latter-day Saints (LDS Church), and their predominant theology is Mormonism. A minority of Latter Day Saint adherents, such as members of the Community of Christ, believe in traditional Protestant theology, and have distanced themselves from the distinctive doctrines of Mormonism.
The movement began in western New York during the Second Great Awakening when Smith said that he received visions revealing a new sacred text, the Book of Mormon, which he published in 1830 as a supplement to the Bible. Based on the teachings of this book and other revelations, Smith founded a Christian primitivist church, called the Church of Christ. The Book of Mormon brought hundreds of early followers, who later became known as "Mormons", "Latter-day Saints", or just "Saints." In 1831 Smith soon moved the church headquarters to Kirtland, Ohio, and in 1834 changed its name to the "Church of the Latter Day Saints."
After the church in Ohio collapsed by dissensions in 1838, Smith moved to Missouri. After Smith's death in 1844, a succession crisis led to the organization splitting into several groups, the largest of which, the LDS Church, migrated to the Great Basin (now Utah) and became most prominently known for its 19th-century practice of polygamy. The LDS Church officially renounced this practice in 1890, so that the Territory of Utah could become a State, and gradually discontinued it. This change resulted in the formation of a number of small sects who sought to maintain polygamy and other 19th-century Mormon doctrines and practices, now referred to as Mormon fundamentalism.
Other groups originating within the Latter Day Saint movement followed different paths in Missouri, Illinois, Michigan, and Pennsylvania. For the most part these groups rejected plural marriage and some of Smith's later teachings. The largest of these, the Community of Christ (originally known as the Reorganized Church of Jesus Christ of Latter Day Saints), was formed in Illinois in 1860 by several groups uniting around Smith's son, Joseph Smith III. Most denominations existing today that adhere to the teachings of Smith have some historical relationship with the movement.
Source: Wikipedia, "Latter Day Saint movement", available under the CC-BY-SA License.