Temple-attending members of The Church of Jesus Christ of Latter-day Saints wear special, ceremonial clothing as part of performing sacred ordinances. The First Presidency has recently announced adjustments to the clothing to make it more simple, comfortable, and cost effective.
These changes aim to enhance the temple experience for patrons as well as make the clothing more affordable to more members. The change in no way alters the sacred nature of temple covenants and the clothing that was previously being used may still be used for temple worship.
Below is a video produced by the Church that explores and explains some of the significance behind the use of ceremonial clothing in Latter-day Saint temples: