The HBU e-mail distribution list is just like any listserv-based list, except that it's hosted by Google instead of a listserv (I do not know of any public access listserv sites!). Just as clubs and user groups have had e-mail lists, IRC groups, and/or Usenet newsgroups for decades, the HBU has its own e-mail list.
With this list, you do NOT need to send to a long list of addresses. Sending to the club's e-mail list will send to everyone in the club who wants HBU-related e-mail. You also do not need to send both to a user on the list and to their individual e-mail address. Depending on each person's e-mail configuration, this could cause duplicate copies of every e-mail (typically for non-gmail.com addresses—addresses on gmail should, as mine does, see the duplicate and delete the extra copy). Based on what I've seen on other lists, some people get really angry over this (as in, HUGE flame wars).
NOTE: You can only post to the HBU list if you are a member of the list.
And that's it. Nice and simple!