In its simplest form, a sportsbook is an entity that accepts wagers on sporting events and pays bettors who win based on the likelihood of those outcomes. It also collects money from those who lose, which is known as the vig or juice. This is how sportsbooks make a profit and cover their overhead costs.

To set their odds, sportsbooks usually hire a head oddsmaker, who relies on information such as power rankings and computer algorithms to determine prices. Odds are then expressed as a ratio that reflects the probability of winning on one side of a bet compared to the other. For example, if a sportsbook offers +110 odds, this means a $100 bet will win $110.

Sportsbooks move betting lines to encourage casual players to place more money on teams with lower winning probabilities. They also move lines to offset correlated action on different bet types. For instance, if they notice a lot of action on the over for Patrick Mahomes’ passing totals, they might lower the over/under line (e.g. from -110 to -125) and raise the over/under line for touchdowns (e.g. from 249.5 to 252.5).

Sportsbooks are regulated in the US, so they must adhere to gambling laws. They must also offer responsible gambling features, such as time limits and warnings. Lastly, they must monitor their customers’ location to ensure compliance with local regulations. This is especially important if they use offshore providers. Offshore providers can expand their reach and add new markets to their offering, but they should be sure to comply with all local laws before doing so.