a means of sending messages by email to many people. Discussion lists are usually maintained by special services, and messages are archived and can be accessed on the Internet. The main provider in the UK for higher education discussion lists is JISCmail.
A group of folks who discuss a stated topic via email. Members of a discussion list (subscribers) communicate by sending posts (email messages) to a centralized source (list server or moderator), which in turn distributes the posts to the community at large, usually by means of specially designed software. Discussion lists range in size from tens to thousands. They are often moderated (to a greater or lessor extent), though many are automatically managed by list servers.
Mostly moderated, these are emailed discussions on areas of interest, often offered by websites. Talk about a way to find a niche market.