The purpose of GAM Repository Namespace is to group in an abstract container all the Repositories that belong to the same Company, or have something in common.
Users defined in a Repository inherit their User Namespace from the Repository Namespace where they were defined. A User can be enabled in another Repository different from where he has been defined, provided both Repositories have the same Namespace.
Executing GAM Backend, an administrator of a Repository can display all the users of the Repository he manages, and he is also able to display the users of the other Repositories who have the same Repository Namespace. There the administrator can enable the User of another Repository in the current Repository (in the Repository he manages).
GAM Repository features and properties
GAM - Repository