A narrow opening into which something can be fitted, such as a hole in the side of a container. A slot is also the name of a position in a group, series, or sequence. In sports, a slot is the area between the face-off circles on an ice hockey rink. The word is also used to describe the position in a schedule or program where an activity can take place.

The earliest slot machines were mechanical reels powered by levers, but modern slot machine manufacturers use electronics to create variations on the original theme. For example, some electronic slots have interactive bonus events and video graphics that engage players. Others feature microprocessors that can multiply payouts and incorporate multiple paylines.

Unlike traditional slot machines, which have only a fixed number of symbols that can appear on each reel, most modern slot machines use random-number-generating software to pick the symbols that stop in each spin. This software combines thousands of numbers within a massive spectrum, and each reel then displays a combination of these symbols. The results of a particular spin cannot be predicted or replicated, and winning remains entirely based on luck.

Slot is a dynamic content element that either waits for content to be placed in it (a passive slot) or calls out to the scenario to fill it with content (an active slot). A slot can reference a repository item to get its content, or it can refer to a renderer to have a specified piece of content displayed in the slot.