A sportsbook (sometimes abbreviated as book) or a race and sports book is a place where a gambler can wager on various sports competitions, including golf, football, basketball, baseball, hockey, soccer, horse racing, boxing, and mixed martial arts. The method of betting varies with the sport and the type of game. The more prominent the event, the more wagering options that are made available.

Winning bets are paid when the event finishes, or if not finished, when played long enough to become official; otherwise all bets are returned. This policy can cause some confusion since there can be a difference between what the sportsbook considers official and what the sports league consider official. Customers should carefully read the sportsbook rules before placing their bets.

The betting volume at sportsbooks varies throughout the year. Bettors have more interest in certain types of sports and increase the money wagered when those sports are in season. Likewise the interest in sports varies by country since the level of interest in the various sports is not constant throughout the world. Some major sporting events that don't follow a specific schedule, like boxing, can create peaks of activity for the sportsbooks.

See also:
UK Sportsbooks
Internet Sportsbooks

Source: Wikipedia