A pillow sham is a decorative cover for a pillow. It often features a decorative flanged border and an opening at the back meant for inserting the pillow. In contrast to a sham, a pillowcase is a simple envelope-style cover for a pillow outfitted with an opening at one end intended inserting the pillow. The main difference between the two is that shams are used to add style to a room, while pillowcases are used to protect the pillow and keep it clean. Oftentimes, pillowcases are used under a pillow sham.