Each user is a member of one or more usergroups.
Some usergroups can be given control over (lesser) usergroups.
For example, a "Sales Manager" usergroup could be given control over a "Client" usergroup. In this case, all members of the "Sales Manager" usergroup can use the User Manager component to edit the login details of the members of the Client usergroup.
The password can be changed, but the current password is not revealed.