A casino is a place where people can gamble and play games of chance. It usually has a bright and cheerful atmosphere with gaudy floor and wall coverings and no clocks, because it is believed that the flashing lights and the sound of slot machines and blackjack tables will make gamblers lose track of time. Many casinos also give free items, called comps, to players who spend a lot of time and money gambling. High rollers, who are known to bet large sums of money, are given extra perks such as free hotel rooms and meals.

Although gambling probably predates recorded history, the modern casino with a variety of ways to gamble under one roof did not emerge until the 16th century, when a gambling craze swept Europe. At that time, aristocrats often gambled in private clubs called ridotti.

While casino gambling was legal in Nevada from the start, it took decades before casinos opened in Atlantic City and New Jersey, and until the 1980s for more American states to allow them. In the 1990s, Native American tribes began opening casinos in increasing numbers, since they are not subject to state antigambling laws.

Due to the large amounts of currency handled within a casino, both patrons and staff may be tempted to cheat or steal, either in collusion or independently. Security measures are therefore very important. Card dealers keep their eyes on their tables to prevent blatant cheating such as palming, marking or switching cards, and pit bosses oversee table games with a broader view to look for patterns of betting that could indicate cheating.