A slot is a placeholder that either waits for content to be added (a passive slot) or calls out for content to be added to it using a scenario action or a targeter. Once the slot has been filled, a renderer is used to determine how that content will be presented on the Web page.

Using a slot to organize deadlines, meetings and work objectives can help teams manage their workflow effectively and meet important goals. In addition, using a slot-based approach when tracking progress on projects can improve team productivity by providing clearer expectations of how long tasks should take to complete.

The slot is a narrow opening in something that allows for insertion or access: a door that has a slot for a key, the slot in a window where a shutter can be opened or closed, the slot in an airplane where luggage can be stored, the slot in a CD player where a disc can be inserted, etc. The term is also commonly used to refer to a time period that is reserved or scheduled for an activity: a conference room that can be booked for a meeting, a flight time that is set by an air traffic control agency, etc.

Psychologists have found that people who play video slot machines reach a debilitating level of involvement with gambling three times as rapidly as those who play other casino games. Researchers believe this is due to the fast pace of the games and the fact that they are very easy to play.