A trusted domain is one that the local system trusts when it comes to user authentication. In other words, if a user or application is authorized by a trusted domain, all domains that trust the authenticating domain accept the authentication.

The trusted domain manages people, groups, and resources on behalf of the trusting domain. The resources that verified users require are located in the trusting domain. (Validated users are those who have been granted access to a domain's resources.) Files, directories, workstations, and printers are examples of these resources.)