Chapter 10 Install and System Administration for FortiOS 5.0 : Central management : Administrative domains
  
Administrative domains
FortiManager administrative domains enable the super_admin to create groupings of devices for configured administrators to monitor and manage. FortiManager can manage a large number of Fortinet appliances. This enables administrators to maintain managed devices specific to their geographic location or business division. This also includes FortiGate units with multiple configured VDOMs.
Each administrator is tied to an administrative domain (ADOM). When that particular administrator logs in, they see only those devices or VDOMs configured for that administrator and ADOM. The one exception is the super_admin account that can see and maintain all administrative domains and the devices within those domains.
Administrative domains are not enabled by default and enabling and configuring the domains can only be performed by the super_admin.
The maximum number of administrative domains you can add depends on the FortiManager model.
See Also
Adding a FortiGate to FortiManager
Configuration through FortiManager
FortiGuard
Backup and restore configurations