A slit or narrow opening, especially one used for receiving something.

A slot is a container for dynamic content on a Web page. A slot is used either passively to wait for a scenario or active to call on a renderer to fill it. You can create multiple slots on a single page, and you can assign different content to each slot. Slots can be created with the Add Items to Slot or Targeter actions, and they can also be filled by a renderer using the Fill Slot action.