A casino is a room or building in which gambling takes place. The precise origins of casino are obscure, but it is clear that gambling in some form has been a part of human society for millennia. Today casinos are large, flamboyant establishments offering an array of games and activities. Many are designed to appeal primarily to the senses, with stimulation through sound and light. Most of the games are based on chance, although there is an element of skill in some cases, such as card playing and roulette. In the twenty-first century, many casinos focus on high rollers, whose betting amounts can run into the tens of thousands of dollars. They offer these customers special attention and comps (complimentary items) to entice them to gamble.

The majority of revenue in modern casinos comes from slot machines and video poker. In a 2002 survey of Nevada residents who admitted to gambling, these two games accounted for more than 50 percent of the money lost. The next most popular were table games such as blackjack and poker, which each attracted around 30 percent of the respondents. Other games, such as roulette and craps, attracted less than 20 percent, and bingo and keno only a fraction of that amount.

A major part of the casino experience is the atmosphere, which is designed to create excitement and anticipation. Many are decorated in bright colors, such as red, which is thought to encourage gamblers to bet more. Smoking is permitted, and alcoholic drinks are easily accessible to players. The casino environment is often loud and chaotic, but it is also fun and social.