In computing, a slot is a dynamic placeholder that either waits for content (a passive slot) or calls out for it (an active slot). Slots work with scenarios and renderers to deliver content to Web pages.

In a land-based slot machine, the player inserts cash or, in “ticket-in, ticket-out” machines, a paper ticket with a barcode. The machine then activates reels that spin and stop to rearrange symbols. When a winning combination appears, the player earns credits based on the payout table. The symbols vary depending on the game theme, but classics include fruits, bells, and stylized lucky sevens.

The odds of each symbol appearing on a given pay line are determined by the probabilities assigned to each symbol by the manufacturer, listed in the machine’s pay table. These numbers are then multiplied by the number of stops on each physical reel to produce a probability that each symbol will appear in a particular position. As microprocessors became more prevalent, manufacturers were able to adjust the weighting of individual symbols. This allowed them to offer a greater variety of possible combinations and increase jackpot sizes.