The all-new Users and Groups Manager enabled the handling of user and group information apart from the configuration. It is a more centralized way and the first time users can be fully be managed. Users are no more just their authentication information - they now have a full account which can have multiple means of authentication.
Users can be assigned to multiple groups. Previously these groups had to be provided by the authentication. The Users and Groups Manager allows the creation of custom groups now.
For more information about the User Manager please checkout the documentation.