A slot is a thin opening in something. You can put letters or postcards through a mail slot at the post office. You can also use a slot to deposit cash in a casino or other place that accepts coins. Slots are usually small and can be made up of different colors. They can be a bit tricky to read, but they are often displayed next to the reels on the machine.
In computers, a slot is a resource that is shared by multiple processes. The process that owns the slot is responsible for using it. If the processor does not use it, it will be freed for other processes to share. The process that owns the slot is usually a kernel function, but it can also be an application program.
A slot is a dynamic placeholder that either waits for content to be added (a passive slot) or gets filled by a scenario. Slots are very similar to renderers, but they are designed for a specific type of content. For example, a slot for Media-image cannot contain text or Solutions content. Using multiple scenarios to fill a slot can cause unpredictable results.