In the United States a sportsbook or a race and sports book (sometimes abbreviated as 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 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. Major sporting events that don't follow a specific schedule, like boxing, can create peaks of activity for the sportsbooks.

Wikipedia contributors. "Sportsbook." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 28 Feb. 2017. Web. 3 Apr. 2017.

Betting exchange
A betting exchange is a marketplace for customers to bet on the outcome of discrete events. Betting exchanges offer the same opportunities to bet as a bookmaker with a few differences. You can buy and sell the outcome, you can trade in real-time throughout the event and you trade out to cut your losses or lock in profit. Bookmaker operators generate revenue by offering less efficient odds. Betting exchanges normally generate revenue by charging a transaction fee.

Most exchanges make their money by charging a commission which is calculated as a percentage of net winnings for each customer on each event, or market. Gamblers whose betting activities have been restricted by bookmakers (normally for winning too much money) are able to place bets of unrestricted size as long as one or more opposing customers are willing to match their bets. The odds available on a betting exchange are usually better than those offered by bookmakers, in spite of the commission charged, because there are smaller overrounds.

In spite of these advantages, exchanges currently have some limitations. Because exchanges seek to concentrate their liquidity in as few markets as possible, they are not currently suited to unrestricted multiple parlay betting. Betfair does offer accumulators but these are limited in number and type: users cannot determine the outcomes contained in accumulators themselves. Some exchanges such as BETDAQ also offer multiples but the exchanges act in the same manner as traditional bookmakers in doing so (i.e. they themselves and not a customer act as the layer of such bets). Exchanges also tend to restrict the odds that can be offered to between 1.01 (1 to 100) and 1000 (999 to 1).

Wikipedia contributors. "Betting exchange." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 12 Dec. 2016. Web. 3 Apr. 2017.