MUD

From Gekkeiju Online

Multi-User Dungeons (MUD) were very popular before the graphical online rpgs came to be. Most MUDs were (and some still are) telnet-based so basically anyone was able to connect to them with a telnet-client. This also meant that MUDs were text-based.

Text-based games are something that probably can scare away nearly anyone of today's gamers, especially all those people who have never even touched anything else than 3d games with state-of-art effects. However, MUDs as they were, had quite often way more features than any of the Graphical Online RPGs currently do.

Another very important thing about MUDs is that most of them are under constant development. This means that new features are added all the time and not in some stand-alone packages that are sold seperately (like most commercial MMORPGs do nowadays). This also allowed some of the MUDs to easily experiment around with some very special and unique features. This never happens with MMORPGs.