Bed sheets come in two main varieties: flat and fitted. A flat sheet is simply a rectangular sheet of cloth, while a fitted sheet has four corners, and sometimes two or four sides, fitted with elastic, to be used only as a bottom sheet. The fitted sheet may also be secured using a drawstring instead of elastic. The purpose of a fitted bottom sheet is to keep it from slipping off the mattress while the bed is in use. A particular way of folding and tucking while making the bed, known as hospital corners, is sometimes used when the bottom sheet is flat rather than fitted.

In its most basic form, microfiber is polyester woven extremely fine. Because microfiber doesn’t stain, they make great sheets for kids, if you’re eating in bed, and for those who sleep with their dog. It’s softer than polyester but less breathable than cotton making it good for cold weather.