A casino is a gambling establishment with card tables for poker, blackjack, craps, and roulette; game machines such as slot machines; and other betting devices. Casinos also feature entertainment such as shows and live music. Casinos can be large, themed resorts or small, standalone building and can be found in urban areas as well as suburban and rural locations. In the United States, casinos earn billions in profits each year for their investors, owners, and patrons. In addition, regulated online casinos are an increasingly significant source of revenue.

A variety of games can be played in a casino, but most have mathematically determined odds that guarantee the house an advantage over players. The house edge is usually expressed as a percentage. In table games such as poker and craps, the advantage is built into the rules of the game; in other games, such as roulette and slots, it results from the mechanical nature of the machines.

Something about the environment of casinos encourages cheating and theft, either in collusion or independently. That is why casinos spend a great deal of time and money on security. In modern casinos, elaborate surveillance systems provide a high-tech eye-in-the-sky that can monitor the entire casino floor at once, adjust for different conditions, and focus on suspicious patrons. The cameras can also be reviewed later for evidence of crime or a violation of casino regulations. In addition, the routines of casino games and the expected reactions of players follow certain patterns, making it easier for security personnel to spot out-of-the-ordinary activity.