Baize is a coarse woollen (or in cheaper variants cotton) cloth, similar in texture to felt, but more durable.
A mid-17th-century English ditty—much quoted in histories of ale and beer brewing in England—refers to 1525:
Hops, heresies, bays, and beer;
Came into England all in one year.
Heresies refers to the Protestant Reformation, while bays is the Elizabethan spelling for baize.
Baize is often used on billiard tables to cover the slate and cushions, and is often used on other kinds of gaming tables (usually gambling) such as those for blackjack, baccarat, craps and other casino games. It is also found as a writing surface, particularly on 19th century pedestal desks.
The surface finish of baize is coarse, thus increasing rolling resistance and perceptibly slowing billiard balls. Baize is available with and without a perceptible nap. Snooker, in which understanding nap effects is part of the game, uses the nappy variety, while pool and carom billiards use the napless type.
For gaming use, baize is traditionally dyed green, in mimicry of a lawn (see Cue sport, "History"), though wide variety of table colours have become accepted. Bay was similar stuff to Baize but lighter in weight and with a shorter nap.