Users can be grouped into a group. Here are some of the reasons you may want to group users:
1. To organize your ticket creators. Not you can also create custom fields for Groups.
2. For reporting purposes
3. [To allow ticket sharing between users in a group using Group Access Rights ](https://help.mojohelpdesk.com/help/article/115429)
4. [To limit access/visibility of a queue ](https://help.mojohelpdesk.com/help/article/244887) (and as an extension a form)