The calendar in this view shows scheduled activity for a particular month, including type and status information.
Different types of activity are shown with distinct glyphs so that you can see at a glance where meetings have been scheduled, or specific timed events rather than dynamically scheduled tasks.
Clicking on an individual day will take you through to the calendar view for that day, with more specific timing and project detail information.
Other user calendars may be viewed, if the permissions and allocated role allows it.