Ack. It's been a while since I've seen gopher in-use anywhere... I've even forgotten a bunch of it. But, I think it runs on port 70 (if memory serves) and its services overlap a lot of what the web is used for today. Very basically, the server end is setup much like a "filesystem" (for lack of a better way to explain it, if nothing else) and the goal is simply to return a set of documents to a querying user. It was a great means for document retrieval for the few months or years it seemed to be taking over, but web applications have since seemed to have nearly put this out of business (similiar to the way that anonymous FTP servers are starting to disappear - though that's also motivated by the obvious security issues).