A casino is a gambling establishment where patrons place bets on games of chance or skill. It is a large business that makes money by offering a mathematically determined advantage over the players, known as the house edge or expected value. The advantage can be very small (less than two percent) but it adds up over the millions of bets placed in a casino, making the casino the winner. The casino profits from this advantage, plus a fee known as the vig or rake and the percentage of funds returned to the players (called payout).

While gambling probably predates recorded history, the modern concept of a casino did not develop until the 16th century, when a gambling craze swept Europe. At the time, aristocrats would gather at private clubs known as ridotti to gamble in a social setting. The concept spread as Europeans changed their laws and adapted the idea to their needs.

Casinos use many different security strategies to keep their patrons safe. The first line of defense is the casino floor staff, who keep a close eye on every aspect of game play to spot cheating and other suspicious activity. Pit bosses and table managers also have a broader view of the games, looking for betting patterns that may signal cheating or theft. Some casinos even have catwalks that allow surveillance personnel to look down on the tables and slot machines through one-way glass.