[Zope] Local or not local roles?

Hello! I was just surfing around into ZMI when into http://dual:27080/some_filename/manage_listLocalRoles i've found this: "To give a user extra roles when accessing this object (and ___its children___), select a user from the User list below, select the extra roles that should be given to that user from the Roles list." Are not local roles setted only in that exactly context? Why it says says "(and its children)"? Thank you, Marco Lazzeri