What is the method used to differentiate an Incident from a Request in the technician request list?

There is an icon there that shows whether it is Incident / Request, but I can't figure out what it is that it is triggered by? Is it some internal flag trigger by which catalogue the ticket is raised from?

The minor thing I'm trying to resolve is that when a ticket notification is sent to the technician we want to have an identifier in the notification to say whether it's a request or incident. I was hoping there was a variable that could be used that just returned 'Request' or 'Incident'.