Or, say if I were your local metropolitan newspaper and sent out a weekly newsletter about what's happening in our town. Or, say, I had a newsletter about what's coming up to read, watch on TV or at the movies, or to do (upcoming local events) about your favorite subject, say science fiction & fantasy?
The best part is, we do this all by email!
Welcome to the world of email newsletters and mailing lists.
Previously, we have discussed email (per se), Usenet, message boards, and chat. Newsletters are unique in that one source (or person) is communicating to many people (like email, Usenet, & message boards) but ONLY to people who have asked to receive the information. Newsletters are a quick and efficient way to communicate either a lot of information or, say, breaking news, with specific subscribers, who usually pay nothing for the privilege. It is like email in that the recipient(s) are known but unlike email in that it is not meant as a personal communication. (It's not real time either, of course, so it's not chat.)
Mailing Lists, and listservs, on the other hand, are still targeted (in that they only go to people who have signed up as subscribers) but the individual postings (opinions) included can come from anyone on the subscriber list. People agree to keep their postings limited to the mailing list's (or listserv's) stated topic, but the resulting "discussion" may or may not be "moderated" (that is, no editor or referee is making sure all are polite and staying on the agreed topic).
A brief word of warning about listservs, though. It's easy to become quickly overwhelmed by the volume of postings on a typical listserv. Yes, you suddenly have access to a lot of information but it may, or may not be, more (in quantity) than you had bargained for!