Administrator can give Password Reset Permission for a group / team, so those who
are in the group / team can manage their own password related problem themselves.
Below screen shot explains this.
In create Helpdesk section the admin can give permission to a certain User,Group
or OU (Helpdesk admin) to reset or unlock a User,Group or OU (Users Managed by helpdesk
In the shown screen shot, the user "TestUser1" can reset / unlock password for the
users in the group "testgroup1".
By default the "Domain Admins" group have the privilege to reset password for anyone.
You no need to add it here,
Don't give "Domain Users" the privilege to reset password reset for "Domain Users"
group, since it means the user can reset the password for the administrator.