Free/busy is a feature that allow others to see meetings scheduled on your calendars. In Calendar preferences, you can define who can see your free/busy information on all of your calendars.
Note: Calendars you created and configured to be excluded from reporting free/busy time are not affected by these settings. No one can see the free/busy time on that calendar.
Allow both internal and external users to see my free/busy information. This is the default. Anyone can see your free/busy times.
Allow only internal users to see my free/busy information. Only internal users can see your free/busy time on your calendars.
Don't let anyone see my free/busy time. Your free/busy time cannot be seen.
Allow only the following internal users to see my free/busy information. Only internal user addresses you list on this page can see your free/busy times.