A slot or slit in which something may be placed: a door with a slot for a lock; a window with a slot for a frame. Also, a position in a group, sequence, or series: a job with a specific duty; a seat on the bus.

In the Ouroboros Praos algorithm, each slot is filled by a leader who constructs blocks in a time window, while the rest of the network waits for the block to finish building. This creates a slot queue, which will eventually be filled by all leaders. Once a slot is filled, the slot leader can begin constructing blocks in a new time window. During this period, the rest of the network is free to wait for the slot to fill again.

A slot is a dynamic placeholder that either waits for content (passive slot) or calls out for it (active slot). It is defined by a scenario, which refers to a repository item or to a targeter that specifies the content to fill the slot. A renderer then delivers the content to the page, as specified by the scenario. For example, a slot might contain a list of events that is displayed in an event-driven interface. Alternatively, a slot might be used to display a dynamic table on a Web page. In some languages, a slot is also referred to as an area. For instance, the area in front of the goal between the face-off circles on an ice hockey rink is known as the slot.