The calendar holds when people are available and what is booked, so an appointment can be offered and taken without somebody phoning back to confirm.
Availability
Availability is what can be offered. It comes from who is working, what is already booked, and the rules you set about when you take appointments.
Getting this right is what makes self-booking safe. Availability that is too generous produces appointments nobody can attend; too restrictive and a customer who was ready to book goes elsewhere. See field team for who is offered.
Appointments
Booking an appointment writes it to the calendar and to whoever is attending.
The value is in removing the gap. A customer who has to wait for a call back to confirm a time is a customer with an unclosed decision, and unclosed decisions are where competitors get in.
Alongside your own calendar
Where Google Workspace is connected, appointments and your existing calendar are visible together, so a booking cannot land on top of something already in your day. See Google Workspace.
The scheduling distinction
Two things use the word calendar and they are different jobs.
This is about appointments: a time agreed with a specific person.
Schedule and dispatch is about the work: which crew goes where, in what order, on a given day.
An appointment creates the obligation; dispatch decides how it gets served. Booking without looking at the second is how a day ends up with three appointments an hour apart at opposite ends of the service area.