Pillowslips, also known as pillowcases, are an essential part of bedding. They protect pillows from dirt and sweat and provide a clean and comfortable surface for heads to rest on. There are many synonyms for pillowslips, including pillow covers, pillow shams, pillow protectors, and pillow sheaths. Pillow covers are typically made of cotton or other soft materials and come in a variety of colors and patterns. Pillow shams are decorative pillowcases with a flange or border that adds an elegant touch to bedding. Pillow protectors are typically made of waterproof materials and help to keep pillows clean and dry. Pillow sheaths are an older term for pillowcases, but still used in some regions.