Their primary function is to protect the dinner table from water marks, food stains or heat damage. They also serve as decoration, especially placemats made from lace or silk. In restaurants they can be used to advertise menu items, specials, local businesses or games for children. If the mat is cotton, it is useful because it absorbs water and other liquids.
Higher end placemats, made from vinyl or leather, are used by hotels and organizations for meetings as they provide a writing surface, and give an area on which to lean comfortably and to place objects on the table with minimal noise during meetings.
Contemporary opinion on the usefulness of placemats is mixed. Cloth placemats are commonly considered to be unnecessary and require excessive upkeep - compared to the surface of a table which can be easily cleaned, a stained placemat must be run through the washer and drier before it can be used again. Moreover, plastic placemats have drawn criticism on environmental grounds.