jockstrap
A jockstrap is a type of male underwear designed for support and protection of male genitals, originally intended to be used in athletics or other activities requiring vigorous physical activity. It is comprised of an elastic waistband attached to a pouch (typically foam), with thigh bands to properly secure it in place.
While it has been mostly used as a utilitarian accessory, foamless or patterned variations have been made to emphasize its appeal as a fashionable and sexual garment. For this reason, both sports and fashion types are popular among gay males.
A counterpart to the jockstrap, known as a pelvic protector or a "jill", is similarly structured to cover female genitals.