A casino is an establishment where patrons can gamble on games of chance. There are numerous games that can be played in a casino, and each game has a different house edge. Casinos are located all over the world, and they are a popular form of entertainment. The casinos in Las Vegas generate the most revenue, followed by Atlantic City and New Jersey. In addition, some American Indian reservations have casinos that are exempt from state antigambling laws.

Gambling probably predates recorded history, with primitive protodice (cut knuckle bones) and carved six-sided dice found at archaeological sites. Modern casinos have many security measures in place to prevent cheating and theft, either in collusion or by individual players. Some of these include video cameras placed throughout the casino, which can be watched in a separate room filled with banks of monitors; betting chips that have built-in microcircuitry and communicate with electronic systems to oversee the amount wagered minute by minute; and roulette wheels that are electronically monitored for statistical deviation.

Casinos make their money by taking a small percentage of all bets placed on their games. This is known as the house edge or vigorish. It is usually lower than two percent and can vary from game to game. Slot machines are the main economic engine of most casinos, generating more bets than any other game and returning a large percentage of the total bets placed. These are simple devices in which the player inserts coins or paper tickets, pulls a lever or pushes a button to initiate a spin of varying bands of colored shapes on reels (either real physical ones or video representations of them). When a winning pattern appears, the machine pays out a predetermined sum of money.