It has both private and public lists on it. Private lists are those lists which are closed to new subscribers unless the list owner adds subscribers to it. Usually these lists will also have private archives accessible only by subscribers. Private lists also usually cannot be reviewed by non-subscribers.
Some commands do the same thing.
Where there are several commands that will perform the same function, these commands are included one after the other. Send the e-mail. Send the e-mail. Send the e-mail. Send the e-mail.