When many people think of gambling, they imagine blackjack or roulette. But slot machines are actually the heart of the industry and bring in more than half of all casino profits. In fact, they’re twice as profitable as all other table games. But what are they really like? What do they do when you press the spin button, and what does it take to win them?

A narrow notch, groove, or opening, as in a keyway in machinery or the slit for a coin in a vending machine. Also: an open position or place in a group, series, or sequence; a berth, billet, or office. He dropped a coin in the slot and dialed. The car seat belt slotted into place easily. A health care provider might use time slots to schedule appointments with patients, allowing them to better organize urgent care and routine check-ups.

A narrow notch or opening between the tips of the primaries in certain birds, which allows air to flow smoothly over the wings during flight. In sports, the unmarked area in front of an opposing goaltender between the face-off circles on an ice hockey rink.