Followers of The Church of Jesus Christ and Latter Day Saints, known as Mormons, may wear any type of underwear they choose. The church's only requirement in regards to clothing worn by its followers is that the clothing be modest.
Most adult Mormons wear special clothing called temple garments. Members wear the garments under regular clothing at all times, and the garments replace regular underwear for some Mormons. Some people refer to these garments as Mormon underwear. Temple garments are actually sacred clothing worn as a constant reminder of the covenant made between the members of the church and God.