The calendar is shared.
If the symbol appears when the pointer is over a calendar’s name, the calendar can be shared.
You added invitees to an event but haven’t sent the invitation, you sent the invitation and no one has responded, or there are mixed responses.
The invitee hasn’t responded to your invitation, but they’re available during the time requested.
The invitee replied to the event or shared calendar invitation as Maybe.
An event set for a specific time. The dot’s colour matches the colour of the calendar with the event.
The Notifications button in the toolbar shows how many new notifications you have for invitations and changes to events and shared calendars.