The point of it is to have a something to link to when folks are asking what the heck this MU*-stuff is all about. So, if y'all are one of the folks who already are familiar with them, feel free to toss in your two cents. If you're one of the folks who aren't familiar with them, feel free to fire off any questions.
Long ago and far away, back in the late 1970s or so, there were games one could play on a pre-Windows computer (Commodore-64, Atari Falcon, Amiga, etc..) that were all text since graphics barely existed and took special hardware to even get something as good as PacMan or Asteroids. One good example of this was 'Hunt the Wumpus'; you're in a network of 12 caves (each one connected to five others), the Wumpus is in one room, you're in another room, there are two bats in two rooms and two pits. If you're one room away from the Wumpus or a bat or a pit, you're told about it (but not which of the five rooms. You'd just get 'I smell a Wumpus!', and you've got a 1/5 chance of heading towards it). You can shoot an arrow into a room to try to kill the Wumpus or make a bat fly away (if you get the room it's in). If a bat ends up in the same room as you (due to you walking into the room or due to the bat getting scared into your room by an arrow), it carries you to a random location. If the Wumpus is in the same room as you (due to the same reasons), you're dead. That was Hunt the Wumpus.
Eventually, folks advanced on the concept in the next decade or so, making such games as the text-only Hitchhiker's Guide to the Galaxy. In those, you still were one player in a number of rooms, but you could interact more with it. If in a room with a ladder, a pear, and a door, you could 'look at the door' and see a description of the door or look at the ladder or pear (or the room itself, or yourself) and see the descriptions for those. You can't pick up yourself, the door, the room, or the ladder, but you can pick up the pear. You can 'go through the door' or 'use door' or 'climb ladder' or 'move up' or suchlike to go through the door or climb up the ladder. Once up or through, you get the description of the new room you're in, as well as exits and contents. This nailed down the text-game code of having Player-objects (you), Thing-objects (that you can pick up or enter), Room-objects (that you can't pick up since they're the environment), and Exit-objects (that lead from room to room) that is still found in MUD and MUSH games (and MUX and MOO and MUCK and the various MU* offshoots. Most of those are just different computer code programs to the same end, like having a word processing program in Apple-Basic and another one in IBM-Basic).
Eventually, some sharp cookie realized that it'd be rather fun to have it so that more than one person could dial up the same game, thus not just interacting with the environment of doors, ladders, and pears, but interacting with other players in the same VR text-space. This led to MUD type games, typically with the premise of it being a dungeon (that's the 'D' in MUD. The MU is Multi-User) that folks were doing the standard D&D fare in, tromping around and hacking up coded monsters and each other (sort've like Quake Arena, if there were chainsaw-toting ogres in there as well, save that it's 100% text so you'd see 'Ogre has arrived', to which you would 'look ogre' 'attack ogre' 'shoot ogre' 'dodge ogre' 'run north' 'run north' 'run north' 'bandage wounds' etc..). For those familiar with ChatRoom RP, it's sort've like this.. Imagine if a chatroom were a single stage in a theatre, and all the actors who are online at the time are on that single stage. Some folks are off in one corner saying they're in a hotel lobby while some other folks in another corner are in a room in the hotel, while still other folks are saying they're standing outside of the hotel on a street-corner. With MUD (and later MUSH), it's like there's one stage for the lobby, another stage for the street-corner outside, one for the stairway up from the lobby, another for the hallway on the second floor, and yet another for each hotel room on that floor. To go from one room to another is sort've like going from one computer to another on a computer network.
A short time later some folks realized that it'd be even more fun if they were to take advantage of this multi-user in a single-environment MUD setting and do some actual honest to goodness roleplaying of characters in there. This 'more talk, less action' style started MUSH RP. That stands for Multi-User Shared Hallucination, with the latter two bits due to how with this pro-RP setup one could just say 'I have a hat on' instead of locating a hat-object (like the pear-object back in the earlier example). Mind, there still often -are- thing-objects, but those are either to save on paperwork (a gun object so that you don't have to keep track of how many bullets you've fired, nor do you have to look up to see how much damage this particular gun does, the range, how it affects the to-hit roll, etc..) or to make things easier in the environment (a car object so four folks don't have to keep walking together in a small group, telling anyone that they pass by, "We're in a car!", like a bunch of kids running around with a cardboard box making Vroom Vroom sounds). More or less, MUSH games and MMORPG (like Everquest) reached a similar end through different paths, although the former is text-based and the latter is graphics based (and might have its roots back in the Dragonslayer arcade video game from the mid 1980s), and the latter is more like a graphic MUD given that it's more a hack-and-slash type of interaction (if a goblin horde is attacking a town in a MMORPG or a MUD, the obvious answer is to attack back. If you have the same thing going on in a MUSH, odds are you'll probably want to try to contact the leader of the horde and try some diplomacy). It's a running joke among MUSH-types that you can spot someone fresh from MUD since their first question is 'How do I kill things?' (PS: The answer? You approach them, RP encountering them, they RP their reaction, you get uppity for some IC reason, and you claim to start to attack them. If it's a qualified MUSH, then they'll pose their reaction to the attack, you pose your reaction to their reaction, etc.. If it's a quantified MUSH, same thing but after you claim to start to attack them, you make a to-hit +roll and they do their dodge or whatnot. After you have the paperwork figured out, the two of you write that up in an action-format instead of just numbers. Then you +roll for your next attack, then pose, etc.. This confuses a number of MUD folks who are used to '@kill bob' '+stab bob' and have the code work it all out, often ending with '"LOL! U R DED! BOB SUX").
Chatroom and Forum (and LiveJournal) RP probably can be traced back to around the same time as such things as the Hitchhiker's game, although that's more from when folks on pre-internet system (such as FidoNet) would write up subsequent chapters to ongoing stories. There was very little direct real-time interaction via computer, so it was more like Forum or LiveJournal RP. With Chat-type programs gaining in popularity those first nabbed the idea of using that computer-setup to RP with, and I believe the FidoNet posting folks eventually realized that Forum Boards could cover what they'd been doing all these years in their weird 'Electronic Play-By-Mail' way. But they've retained the 'one big stage' arrangement as opposed to the 'multiple stage' that MMORPG, MUD, and MUSH have.
Try here.. http://home.comcast.net/~evilrasheem/TUTORIAL.HTM ..for further details. Or here.. http://www.visi.com/~gyles19/homer/carefeed.html