When deployed as a local FortiGuard Distribution Server (FDS), FortiManager functions in several capacities.
It can act as an update server, a rating server, or both, providing firmware updates and FortiGuard database updates. Additionally, it plays a crucial role in VM license validation services, ensuring that the connected FortiGate devices are operating with valid licenses. However, it does not support rating requests from non- FortiGate devices nor cache firmware updates for unmanaged devices.
Fortinet FortiOS Handbook: FortiManager as a Local FDS Configuration