This isn't a great description but off the top of my head:Staff is a staff person's account, or employee of the company that is using osTicket to track client issues. They can belong to a Department, Group, and/or Team.  They have tiered access to do things based upon what Group they are part of, Department they belong to, and any Teams they belong to.  This is the account used by staff to log into the system.Departments are an organizational unit . Tickets are assigned to departments and as such a staff's department determines which tickets they can see and work on.Groups are a security mechanism and are used to assign permissions to groups of users.  Things like "Can Create Tickets", "Can Edit Tickets", "Can Post Reply", etc. Groups can also control which departments group members can see.Teams are a loose connection of Staff accounts that can be comprised of people from different departments. For example you could put Nancy from Support with John from Billing into a team to work on a project together as a way to transcend the security imposed by departments.

Very welcome. :)