A coaster, drink coaster, beverage coaster, or beermat, is an article used to rest beverages upon. The main purpose is to protect the surface of a table or any other surface where the user might place their beverage.
Public houses usually will have beermats spread out across the tables. They are used not just to protect the surface of the table, but, as they are usually made of paper, they can also be used to absorb condensation dripping along the glass or serve as an ad-hoc notepad. Beermats are often branded with trademarks or alcohol advertising. Beermats are not to be confused with bar mats, rectangular pieces of rubber or absorbent material used to protect the counter top and soak up spilled drinks in a bar or pub.