The Workorder Item Summary Template field in Global Settings is where you set what information from a service workorder item to display on the Schedule screen when you hover your mouse over a scheduled workorder item.
See also:
How do I edit the Workorder Item Summary Template Editor for popup on the Schedule Screen?
Below identifies the tags available for the Workorder Item Summary Template field in Global Settings - what each equates to in the workorder item itself.
[O.Client] - the name of the client of the scheduled workorder
[O.WorkorderCategory] - the workorder category selected in this workorder
[O.WorkorderItemScheduledUser] - the scheduled user of this workorder item
[O.WorkorderStatus] - the workorder item status of this workorder item
[Workorder.Label.CustomerContactName] - the Contact text entered in the workorder
[Workorder.Label.CustomerReferenceNumber] - the Reference # text entered in this workorder
[Workorder.Label.InternalReferenceNumber] - the Internal Reference # text entered in this workorder
[Workorder.Label.Onsite] - displays True if Onsite is checked, or False if Onsite in the workorder is not check-marked
[Workorder.Label.Summary] - the Workorder Summary text entered in this workorder
[WorkorderItem.Label.TechNotes] - the Service Notes text entered for this workorder item
[WorkorderItemScheduledUser.Label.StartDate] - the Start Date/Time for the Scheduled User of this workorder item
[WorkorderItemScheduledUser.Label.StopDate] - the Stop Date/Time for the Scheduled user of this workorder item
[WorkorderService.Label.InvoiceNumber] - the Invoice # text entered in this workorder
[WorkorderService.Label.ServiceNumber] - the service workorder number of this workorder