Small cork coaster used to rest beverages on.
Beer, coffee, and tea are wonderful beverages, but if they spill or if the mug they're in leaks and dribbles small amounts of the liquid onto the table, they can get quite messy, leaving behind unsightly stains on the spot they sat on. Coasters (sometimes referred to as beermats) are used to avoid this. Cork or paper is used due to their absorbent properties, as well as their ability to have beverage brands or logos printed onto them. They are even collected by some people, who refer to this practice as 'tegestology'.
Commonly used in bars, restaurants, and residential dining tables.