In a casino, patrons gamble by playing games of chance or, in some cases, skill. The games are operated by live croupiers or mechanical devices (such as roulette wheels and slot machines). They generate revenue for the casinos through bets and wagers placed by customers. Casinos are usually owned by private companies, investment firms, Native American tribes or state governments. The most successful casinos rake in billions of dollars each year for their owners and investors.

The precise origin of gambling is unknown, but it is believed to have existed in every society. Archaeological evidence suggests that wooden blocks were used in games of chance in 2300 BC China, and dice appeared in Rome around 800 AD. Card games appeared in medieval Europe, and by the 1600s baccarat was established as a popular game in many European countries.

Most casino games have built-in advantages for the house that ensure it wins over the players in the long run. These advantages, known as the house edge or expected value, are mathematically determined. In games that have a degree of skill, optimal play can reduce the house edge to near zero. For games such as blackjack and craps where players compete against each other, the house earns money through a commission called the rake.

Casinos have extensive security measures to protect their patrons and property. They monitor video surveillance systems and have employees patrolling the floors, observing patrons and watching for suspicious behavior. In addition, a large portion of the casino workforce is dedicated to the policing of table games and slot machines. Security staff are trained to spot blatant cheating such as palming and marking cards or dice, and they also check to see that dealers are following the rules of their games.