This is the main calendar in the Schedule screen from which you can view information.
The Schedule screen can display two different items for schedulable users - Schedule Markers as well as Workorder Items
You can place your mouse over the item on the Schedule calendar to “pop up” a window providing even more information.
You can edit what displays and does not display in this popup window by editing the settings in the Administration Global Settings.
See also:
Workorder entry screen menu items - Follow Up
Global Settings - Workorder Item Summary Template
How do I edit what pops up on Schedule screen for workorder item?