A sham goes over a pillow and its main purpose is decorative. It typically has some sort of border to enhance the look of your pillow. Shams are meant for pillows that sit on top of a made bed. Shams and duvet covers are a quick, easy way to change up the look of your bed setup with the seasons.
Unlike regular pillowcases, which have an opening on one end, most pillow shams have an envelope flap in the middle or hidden zippers to conceal the opening for a more finished top-of-bed look.