What is Mailing List(Question mark)?

A mailing list is a collection of names and addresses used by an individual or an organization to send material to multiple recipients.
Two different types of mailing lists
Announcement list
where a "mailing list" of people was used as a recipient for newsletters, periodicals or advertising and traditionally this was done through the postal system and now popular is E-mail
Discussion list.
allows members to post their own items which are broadcast to all of the other mailing list members.

A mailing list is simply a list of e-mail addresses of people that are interested in the same subject, are members of the same work group, or who are taking class together.The key advantage of a mailing list over a things such as web-based discussion is that as new message becomes available they are immediately delivered to the participants' mailboxes.