A casino is a building or room where people play games of chance or skill. Casino games include poker, blackjack, roulette, craps, and slot machines. Some casinos also have sports betting and horse racing. Casinos are owned and operated by governments, private corporations, or social clubs. They generate billions of dollars each year for their owners, investors, and customers. Casinos employ many security measures to deter crime. They may use cameras, guards, and rules of conduct. Some casinos have special rooms for high-stakes gamblers, separate from the main floor. These rooms are designed to deter cheating and are often equipped with specially trained personnel.

Gambling in some form has been part of human culture throughout history. The precise origin of gambling is unknown, but it was probably widespread in prehistoric societies. Ancient Mesopotamia, Greece, and Rome all had casinos. The modern casino began to develop in America after legalized gambling was established in Nevada in 1931. Casinos soon spread to other states, with Atlantic City and New Jersey leading the way. Iowa allowed riverboat casinos, and some American Indian tribes operate casinos.

Most casino games have a built-in advantage for the house, which is known as the house edge or vigorish. The advantage can be as low as two percent, but over millions of bets it adds up. The casino edge is especially noticeable in games such as roulette, where the house takes a larger percentage of winning bets than in other games. Casinos compensate for this by giving away free goods or services to players, called comps. These may include hotel rooms, meals, show tickets, or even airline tickets.