A slot machine is a casino gambling machine that creates a game of chance for its customers. Its standard layout is a display with three or more reels which rotate when a lever is pulled or button pushed. Slot machines are also known as one-armed bandits because they were originally operated by pulling upon a large mechanical lever on the side of the machine (as distinct from the modern button on the front panel), and because of their ability to empty a player's pockets and wallet as a thief would. Many modern machines are still equipped with a legacy lever in addition to the button.
Slot machines include one or more currency detectors that validate the form of payment, whether coin, cash, or token. The machine pays off according to patterns of symbols appearing on its display when it stops. Slot machines are the most popular gambling method in casinos and constitute about 70 percent of the average US casino's income.
Digital technology has resulted in variations on the original slot machine concept. Since the player is essentially playing a video game, manufacturers are able to offer more interactive elements, such as advanced bonus rounds and more varied video graphics.