This is the name that the user logs into your network with. Your user will normally have to configure the name into their authentication client software. To log in, they must enter the user name exactly as shown. It is not possible to change a users User Name with the Edit a User. To change a User Name, you would have to delete the old user and add a new one with the correct name.

Your RAdmin administrator may have configured a default value for this field to provide the normal realm for your organization.