While there are thousands of ongoing newsgroup discussions about different subjects, there are also thousands of e-mail list discussions happening as well. Newsgroups are public discussions that anyone with a news reader can subscribe to and participate in. You read what other have written and post your own reply. A mailing list, on the other hand, is simply a list of e-mail addresses of people interested in the same subject.
Someone sends out a message and it goes to everybody on the list.
You can reply to the messages, send new messages, or just lurk, reading the messages without participating. It's up to you. Each time you or anyone else on the list posts a reply, it's distributed to the e-mail box of everyone else on the list. The two most frequently used MLMs are Listserv and Majordomo . The key advantage of a mailing list over a newsgroup is that instead of having to go somewhere to read or retrieve the contents of a discussion, it is automatically sent to you via e-mail.