Bulletin Board Systems, or BBS, are one of the oldest methods of communicating with a larger group. Users could subscribe to a group and read, post, and reply to messages. The BBS is limited to text messages, but could include attachments.Newer newsreaders will display the attachments with the post.
Early BBSs were hosted by individuals and were therefor dependent on the users machine being online, but were later hosted by Internet Service Providers.
It is from the BBS that Usenet and the newer web-base internet forums developed.
The educational relevance as a collaborative tool has come and gone with newer technologies, but remember the BBS next time you look at the forums in WebCT.