What Is a Sportsbook?

A sportsbook is a specialized service that offers bettors a wide range of betting options on sporting events. It is at the heart of many online gaming brands and frequently comes accompanied by a racebook, casino, live betting, and video games.

Betting lines at a sportsbook are set by an oddsmaker and often rely on data, computer algorithms, and outside consultants to establish prices. They can be presented in three ways: fractional, decimal, and American odds. American odds are based on $100 bets and can differ across sportsbooks. For example, a team may be -180 at one book and -190 at another, resulting in a small difference of.10 cents that won’t break a wager but can add up over time.

The goal of a sportsbook is to attract a balanced amount of action on both sides to minimize potential liabilities. In practice, this is rarely achieved, and sportsbooks will shift betting lines in a number of ways. For instance, if they see that a line is opening with lopsided action, they will move it to balance the action and reduce their risk. They also adjust lines as more information becomes available (e.g., injury or lineup changes) and to offset a negative expectation.