A casino is a facility where gambling activities take place. The term may refer to a specific building or to an entire complex. It also may refer to an organization that runs such a facility. The precise origin of gambling is unknown, but it has been present in almost all human societies.

Modern casinos offer a wide variety of games of chance and skill. Many of these games have mathematically determined odds that ensure that the house always has a long-term disadvantage, although players may occasionally win large sums. Some of these games have an element of skill, and the skills of advantage players can eliminate the disadvantage. Some casinos specialize in certain types of games, such as baccarat and blackjack, which attract high rollers. Others have a broad range of games and attract casual gamblers. Still other casinos focus on non-gambling entertainment and provide hotels, restaurants, bars, non-gambling game rooms, spas, and more.

Because of the large amount of money that is handled, security in casinos is a major concern. Casinos use cameras to monitor patrons and employees. They also employ specialized security forces, who patrol the premises and respond to calls for assistance or reports of suspicious or definite criminal activity. In addition, casinos take steps to prevent cheating and stealing by customers and staff. They also display brochures about Gamblers Anonymous and other treatment options near ATM machines and pay phones. Some casinos have adapted these measures to their online operations.