Appointments+ - Does each user set up their own Google Calendar?

I have the appointments+ plugin working well right now. Yay!

I am adding a new user to the site, who offers services. In the Plugin Settings, everything looks just right.

In the user's profile, toward the bottom, it gives the option to sync with google calendar.

Does this sync their appointments with their own personal calendar? As a provider? As a client?

How is it different from the main set up of the Google api, etc. in the settings of Appointment +?