This is a short article that attempts to explain what BNF is, based on message <wkwwagbizn.fsf@ifi.uio.no> posted to comp.text.sgml on 16.Jun.98. Because of this it is a little rough, so if it leaves you with any unanswered questions, email me and I'll try to explain as best I can.
It has been filled out substantially since then and has grown quite large. However, you needn't fear. The article gets more and more detailed as you read on, so if you don't want to dig really deep into this, just stop reading when the questions you are interested in have been answered and things start getting boring.