The purpose of underwear is to cover the genitals and keep them warm. The purpose of diapers is to absorb urine and feces. Underwear is made of cloth or synthetic material, while diapers are made of absorbent material, such as paper or cloth. Underwear is typically less expensive than diapers, and can be used more than once. Diapers must be disposed of after each use. Underwear can be worn by people of any age, while diapers are typically for babies and young children. Underwear is less revealing than diapers and is more discreet.