A casino is a building that houses gambling games. People visit casinos to play slot machines, craps, blackjack, roulette and other games of chance for the billions of dollars a year they bring in. The profits from these games give casinos the money to build hotels, shopping centers, fountains and replicas of famous pyramids, towers and landmarks. A casino is also where many people go to meet friends or to have a romantic evening.

Casinos make their money by putting the mathematical advantage of the house into every game offered, whether it is a roulette wheel, a slot machine or a table game like poker or baccarat. This edge is very small—usually less than two percent—but when multiplied by the millions of bets that are placed in a casino, it can add up to substantial sums of money.

Because of this, casinos are choosy about whom they let gamble with them. They focus on “high rollers,” whose bets can run into the tens of thousands of dollars, and offer them free spectacular entertainment, hotel rooms and even limo service and airline tickets. Casinos also have comp programs for lower-stakes players that offer free food, drinks and show tickets.

Gambling probably predates recorded history, but the modern casino is thought to have started in the 16th century, when a gambling craze swept Europe. Until 1978, when Atlantic City opened, most American states banned casinos. However, during the 1980s and ’90s, casinos began to appear on Indian reservations in states that did not prohibit them. Today, there are estimated to be more than 3,000 legal casinos in the United States alone.