A slot is a narrow opening in a machine or container, especially one into which coins may be inserted.

Traditionally, slot machines require a coin or paper ticket with a barcode to be inserted into the machine and activated by a lever or button (either physical or on a touchscreen). When activated, reels spin and stop, ultimately displaying symbols in a pattern that matches a payline — winning credits are awarded according to a payout table. Symbols vary by game but classic symbols include fruit, bells and stylized lucky sevens.

Modern slot games use a random number generator (RNG) to determine the sequence of symbols that appear on the reels with each spin. Because the RNG has no memory, the results of each spin are independent of those that came before or after it, ensuring that each spin is an independent event. Because of this, predicting the result of a spin is impossible.

Although casinos have the ability to increase the house advantage of slot games, they must be cautious not to do so too much. If the house edge becomes too great, players may defect to another casino. In addition, it is difficult and expensive for a casino to recover from the loss of customers. Instead, casino operators often opt to raise the house advantage in small increments over time to maximize revenue. This approach is also known as incremental price increases. See also pricing strategies, price signals and elasticity.