A casino is a gambling house where customers gamble using cash or other items of value on various games of chance. Some casinos also offer skill-based games such as poker and blackjack, and pay out winnings in the form of comps (free food and drinks) or money. Casinos are most often found near or combined with hotels, restaurants, retail shops, and cruise ships. They may also be located on various American Indian reservations, where gambling is legal under state law.

While gambling almost certainly predates recorded history, the casino as a place where patrons could find a variety of ways to gamble under one roof did not emerge until the 16th century. During that time, a gambling craze swept Europe, with Italian aristocrats gathering at private clubs called ridotti to play cards and throw dice. Although the clubs were technically illegal, they were rarely bothered by the authorities.

Modern casinos use technology to enhance security as well as to improve game rules and odds. In table games, for instance, casinos keep track of each players’ betting behavior and reactions to ensure that the casino is not being cheated; they also monitor payouts minute by minute to discover any statistical deviation from expected results. Dedicated mathematicians and computer programmers who study the statistics of casino games are known as gaming mathematicians or analysts. Their work is used to calculate the house edge and variance of casino games, both of which tell casinos what kind of profit they can expect to make as a percentage of total turnover.