Within Teamwork Desk you can set up your own ticket types in addition to the default ones in Desk.
To set these click on your profile icon to the top right of the Desk navigation bar and choose 'Settings' from the dropdown:
Select 'Company' from the available settings options:
Once in the Company settings in the left-hand pane, you will see the option for 'Ticket Sources':
You can then view existing sources such as 'Docs', 'E-mail' and 'Phone'. If you want to add another, enter the details into the box at the bottom and click 'Add' to the right.
Note: Only administrators on your Teamwork Desk account can add/edit or delete ticket sources.