Privileged
The group Privileged is one of the three groups for which RT manages the membership automatically. The other two are Unprivileged and Everyone. Every user is either a member of the Privileged group or of the Unprivileged group. Membership in the Privileged group means a user can be granted rights. To which one a user belongs can be set in the configuration screen for the user using the 'Let this user be granted rights' checkbox.
To resume:
- unprivileged -> access to SelfService only (whatever Rights are)
- privileged -> access are controlled by Rights