Sure, although it’s not all that “secret.” You can ask any Mormon about it. The “garment” as it is commonly called, is a symbol of their dedication to God and the religious promises that they have made. It is conferred, somewhat like a religious habit, in a temple ceremony known as the “temple endowment.” This is when they are instructed in what the garment is and what is stands for and how it should be cared for. The garment is worn under other clothing next to the skin, reminiscent of the first garments that God made for Adam and Eve as they were expelled from the Garden of Eden. Thus, for many Mormons, their garment takes the place of regular underwear. The garments are made at official LDS clothing centers and made available through their very well developed LDS distribution centers for purchase by LDS members in good standing. There is actually a website dedicated solely to the subject. If you want to learn all about it, go to http://www.mormon-underwear.com/