Within Alldevice you can assign departments to the tree structure, see below picture can be assigned a department, and access to the departments can be restricted with the user setup.
It could be you have restricted areas, or 3rd party maintenance for certain devices and you wish to limit visibility.
If you select a level from the device tree on the right using the right click you can then select departments, this shows a list of departments setup, and you can see if a location is assigned a department.
Depending on the department settings in the device tree & the User settings the views can be limited, below shows the User settings where access to Department 1 to 4 is visible ie all devices in those locations can be seen by this user.
Usergroups can also be used to pre define the rights of a group, and often is used in conjunction with Departments to ensure only the actions needed are possible for that group, for example below is a screenshot of a Usergroup 'Subcontractor' where only the selected actions needed are set, this Usergroup is assigned to all Subcontractor users when setting them up.
