A listserv is a discussion group comprised of people with shared interests.
Membership is by subscription, and messages arrive in regular e-mail.
One can reply to the whole list or send private messages to someone who is asking a particular question. Listservs vary greatly in the amount of activity they generate. Listserv traffic can be archived. This means that a message you read and discarded a month ago can be retrieved from the central site of the listserv now that you need it, or that information from before your joining the list is retrievable. One service Media Specialists can provide to their students, faculty and administrators is to identify subject area listservs of interest.