Terminology
Reservation
A Reservation entity represents a guest (or group of guests) who are planning to stay in a specific room during a specific time frame.
Visit
A Reservation is turned into a Visit once at least one guest arrives and checks in.
Span
A Span is a specific block of time where one or more guests are staying. A visit can have multiple spans. A new Span may be created when a guest changes rooms, changes room rates, or goes On Leave.
Stay
A Stay represents a single guest staying in a Span. This may span the whole Span, or end prior to the Span ending, if the guest checks in after the span start, or checks out prior to the span ending.
On Leave
A span with a status of On Leave means that the guest(s) have gone home for a few days and are not staying at the house during that time, but their room is reserved. Other guests cannot stay in that room while a Span is On Leave.