A sportsbook is a gambling establishment that accepts bets on various sporting events. Typically, they accept bets on either side of an event and can profit by the difference between what is wagered and the amount won. In the United States, sportsbooks were only legal in Nevada and in limited forms in Oregon, Montana, and Delaware before a Supreme Court decision in 2018. Since then, more than 20 states have made betting on sports available, with some offering online access.

While sportsbook odds can be confusing, understanding how they’re set will help you make better choices. Most sportsbooks use a third party to set their odds, but promotions and other factors can influence prices. American odds, for instance, are based on a $100 bet and can vary from one book to the next.

Besides setting the lines, a sportsbook needs to pay out winning bets. This requires a lot of cash, which is why the majority of their profits come from vig. Essentially, a sportsbook collects a percentage of all losing bets and uses it to cover overhead costs and pay out winning wagers.

Sportsbooks are also making a big profit from sports leagues. Nearly every major league has signed a sponsorship deal with a sportsbook, including the NFL and NBA. These deals have boosted revenue for the sportsbooks and have been controversial in some cases because of the NCAA’s stance against betting on college games. However, sportsbooks are not able to control the problem on their own, and it is important for governments to regulate them and make sure that they are operating legally.