A casino is an establishment for gambling. It can be located in a city, town, tourist attraction, cruise ship or on a riverboat. Casinos often offer table games, slot machines and poker, and sometimes sports betting. The exact origin of gambling is unknown, but it has been present in human societies for millennia.

In the United States casinos are legal in 40 states. The largest concentration is in Las Vegas, followed by Atlantic City and Chicago. The number of casinos is growing, as more states seek to legalize them. This expansion is due to interstate competition and the appeal of casino tourism to local residents.

Modern casinos are often modeled after Las Vegas resorts and feature elaborate themes, entertainment, shopping and restaurants. However, most of their profits come from games of chance. Slot machines, blackjack, roulette and craps are standard casino games. Other games may have elements of skill, but the house always has a mathematical advantage over players. This advantage, which can be quantified as expected value or the house edge, is what keeps casinos in business.

Because of the large amounts of money handled in a casino, both patrons and staff may be tempted to cheat or steal, either individually or in collusion. To counter this, most casinos employ a variety of security measures. The most basic is a network of surveillance cameras that monitor all areas of the casino. More sophisticated systems allow security personnel to watch multiple screens in a separate room filled with banks of monitors.