Knowing what types of bed sheets fit your needs can help you sleep better and prevent you from having to buy replacements every few months. When choosing your sheets, keep in mind what type of sleeper you are. Hot sleepers are better off with breathable, cooling sheets like cotton or linen, while cold sleepers should opt for something warmer like flannel. Also, consider how much they will be used and what type of people (or animals) will use them the most. 

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.