A casino is a gambling establishment where people can play a variety of games of chance. Casinos can be found in the United States and many other parts of the world. Most casinos are located in cities or near major tourist attractions, and some are even built into hotels.

The precise origin of gambling is not known, but it is believed that casino games are as old as human history. The first modern casinos appeared in the 16th century, when a gambling craze swept Europe. Aristocrats would often gather in private places called ridotti to gamble and drink, but the legality of these venues was sometimes questionable.

Today, there are more than 3,000 legal land-based casinos in the world. The largest casinos are in Las Vegas, Nevada; Atlantic City, New Jersey; and Chicago, Illinois. Other popular casinos are in Reno, Nevada; Biloxi, Mississippi; and Macau, China. Some American Indian reservations also have casinos, which are exempt from state antigambling laws.

Because large amounts of money are handled within casinos, security is a high priority. Casinos employ a variety of security measures, including cameras and trained personnel. Some casino security measures are obvious; for example, players at card tables must keep their cards visible at all times. Other measures are less obvious; for example, the routines of casino games create patterns that can help security staff spot unusual activity. In addition, casinos reward frequent players with comps (free goods or services), such as free hotel rooms, meals, show tickets, or even airline tickets.