A mailing list can be thought of as an alias pointing to groups of users, which allow mail to be sent to the whole group at once. Mailing lists are often set up to carry certain topics.
Internet mailing lists often follow a convention for having a separate
alias for administrative aspects of mailing list management. This
convention consists of adding a -request to the local part of
the mailing list address.
As an example, consider mobile-ip@parc.xerox.com mailing lists
which discusses extensions to the Internet Protocol to accomodate
mobility of hosts. In order to subscribe to this mailing list, one
simply can send a message to mobile-ip-request@parc.xerox.com
asking to be added to that mailing list.
It is good practice to keep a record of mailing lists to which you subscribe. Having that information comes very handy when you need to change your e-mail address.