Staff accounts have both an assigned group and assigned department. Both of these indicate which tickets a user has access to see/edit/update/close/etc. You can see what group and department your account is assigned to by going to:
admin panel -> staff -> staff members -> your account
Look at Assigned Group and Primary Department.
You can then go to:
admin panel -> Staff -> departments -> your accounts department
see the Department section (which has check boxes)
admin panel -> Staff -> groups -> your accounts group
see the Department section (which has check boxes)