Pillowcases are made of the same material as bed sheets. Most sheet sets come with two pillowcases in the same color and fabric as the sheets. While pillowcases are designed for sleeping, pillow shams serve a more decorative purpose. Pillow shams are typically made of a heavy, coarser material that matches the bedspread or duvet cover. Depending on the fabric, pillow shams may not be comfortable for sleeping. Pillow shams also have a slit that runs across the middle of the back of the pillow and often closes with an overlapping piece of fabric.