Bulletin board - a term with two related meanings. First, it is a public discussion area where people go to post messages that can be viewed by any one who enters the area. It is like e-mail but the message is sent to a public posting area rather than to an individual or list of individuals. It requires the server computer to run special software and may or may not allow users to access the Internet. Most bulletin boards must be dialed directly via your computer's modem rather than connecting to the BBS through the Internet.
Some courts operate bulletin boards where users can dial in and get slip opinions etc.
On the Internet, the equivalent areas are called newsgroups. Second, some commercial services use the term to describe their on-line discussion groups. Top of Page C Compression - pretty much what it sounds like. The process of condensing information so that it can be stored in less space or transmitted in less time. Some data files use more bandwidth as they are transmitted over the lines.