A sportsbook is a gambling establishment that accepts bets on various sporting events. In the United States, the only legal sportsbooks until 2018 were in Nevada (and then in limited form in Montana, Oregon and Delaware). But with betting on sports now legal in 30 states, the number of options has expanded significantly. Most online sportsbooks also allow you to place bets from your home.

Most of the betting action at a sportsbook revolves around the odds on an event, which are generally set by a head oddsmaker, who uses information from sources like power rankings and outside consultants to create prices. In American markets, the most common way of presenting these odds is in ratios that reflect how much money you could win with a $100 bet. The odds are usually positive (+) or negative (-).

Odds for next week’s NFL games start taking shape each Tuesday at a handful of sportsbooks, known as “look ahead” lines. These are based on the opinions of a few smart sportsbook managers but typically do not factor in any significant early limits from sharps. But when the real betting action begins on Sunday afternoon, the sportsbooks’ early look-ahead lines often get pulled or slashed in an attempt to deter action from winning players.

In addition, the rules governing how a sportsbook pays out winning bets can vary from one betting house to another. For instance, some sportsbooks treat pushes as losses, while others will return your original bet amount plus a percentage of your winnings.