In FHIR the “slot” resource is simply a specified duration linked to a schedule that may be available when booking an appointment. Slots can only provide length of time allocations that can either be free, and therefore available to book, or busy; if required slots can be allocated to specific use cases.

Additionally, a slot can also be marked as busy without any appointment being attached to it e.g. unavailable, or busy tentative if an appointment has been reserved but not confirmed.

A slot can have more than one appointment allocated to it if a schedule has been created to allow for multiple appointments for the service at the same time e.g. for a group session. These type of slots require the addition of a specific number of places available.

A slot can be simplified as When.