As you can possibly tell from the name, a MUD is played by several people at the same time. They run around in a computer controlled environment of some form and do some sort of activity. In some cases this activity is like your average D&D campaign, in other cases there is more emphasis on role playing and puzzle solving. The world can also be controlled and changed by the people who run the MUD. This is one of the other big factors in a MUD, it is possible for you to make changes which many other people will see. In general the D&D style MUDs seem to be the most popular, however the role playing MUDs have been around for a long time and don't seem to be disappearing, there just appear to be less of them.
An example of a committee run MUD is Discworld. It has several levels of decision making people, and the tasks they are supposed to perform are set down quite well. There are four levels of people on the mud, the players, the creators, the lords and the high lords. The high lords are the ones with the ultimate decision making ability. They make decisions about things which effect the MUD as a whole, any MUD wide bugs or problems that come up, these are the people who should fix them. The lords are all in control of a section of the MUD. They look after and make any decisions needed for their section of the mud. The creators are responsible to a lord, who organises them and helps them with any problems. Creators are usually given even smaller slices of areas to look after, although this is completely up to the lord of the domain in which they are in. Their main function is not to co-ordinate (like the lords and high lords) but to actually build new areas of the mud and to find bugs in old areas of the mud. The players are the ones who have the fun (in theory), they play with all the things which the lords, high lords and creators have done. This system works fairly well, however it breaks down in a few ways. Since a lord looks after an entire region and they cannot be on at all times, it makes it difficult for them to look after creators from other time zones. There are often times where there is no high lord on at all, which means that some mud wide problems can exist for quite some time before they are fixed. Theoretically (and in practice) it works a lot better than the old standard mud system. Since the original system was designed for Discworld it has been extended a bit. There is now a provision for a liaison lord and liaison creators who sole function is to look after the players interests. To see that the players do not get lost in the system. The other position which has been created since the start is the position of an independent creator. They do not work for any specific lord and have much more freedom in what they write and create.
The standard mud system is usually an Autocratic one. You have one person in the top position, usually calling themselves a god, under this you have the Arch Wizard position's, who act very like the high lord position, and then the Wizards. The Wizards look after a small section of the mud, just the bit they built themselves. This leads to problems if for instance the Wizard leaves the mud and does not return, no one will upkeep their area. If the Autocrat leaves the mud, then there is the problem of who to replace them with, or if they should change the system totally to start running it with a group of people in the top position. This indecision has been the death of several MUDs.
On some MUDs the people in the Arch Wizard position are divided into several groups. There is one Arch Wizard that looks after the Law and order of the mud specifically, they deal with fights between players and rapes of female characters (which usually ends up being by far and away their biggest concern). Another Arch looks after the Source code of the mud, making sure it all works and that the MUD does not crash or go down for significant periods of time. One more Arch looks after the Balance of the game, making sure that not too much money is getting into circulation, or that people are not gaining levels too quickly. Generally making sure that people who play the game do not get way too much more powerful in one way or another than other people who are playing the game. The last position is Quality Control, they look at all the areas which Wizards are trying to enter into the game to make sure that the descriptions are of a high quality and that the code will not break very easily. Another position that is often set up in a MUD is the position of Wizard Helper, the Wizard Helpers look after the Wizards and deal with any coding problems they might encounter (or any other problems for that matter).
The position of Wommon in MUDs is at least as bad as Wommon in our society, however on a MUD they can hide their sex and thereby rise to positions they would not normally have been able to achieve. An interesting experiment is to log into a mud (it generally helps if the MUD has quite a few people on-line) as both a female and as a male character. I tried this on Discworld and was quite shocked to find my female character was abused within about 5 minutes of logging on. I got some tells from a male character saying some quite explicate things. The fact that this occurred so quickly, yet as an administrator I hear so little about it, tends to make me think that it is more common than I imagined and/or that people do not report it as they do not think it will be taken seriously. As a male character I also got more offers of help and assistance than I did as a female character. It is possible to use this sexism against the people who do it to the female characters, a friend and I both logged into a MUD as female characters and managed to get several of the 'big tough males' on the MUD to get us a lot of equipment by pretending to be weak and helpless etc. However I found it quite degrading to have to do this to get this equipment that I have no desire to try it again. If you are a woman and you do try and be assertive and hold up your rights, you often get branded as a bitch. Rumours will suddenly spring up about you and dash around the mud like wolves with their heads cut off.
The position of wommon in MUDs is a sad reflection of today's society.
Once you have logged into a MUD, one of the first things you should do it type help this will give you a starting point from which to find all of the commands which you can use on this MUD. I think I shall stop giving you a guided tour of the MUD form here and just talk generally about things you can do.
There exists on a MUD many different methods of communication with other people in the MUD. There are methods of telling just one person a message, lots of people a message and selected groups of people a message. As MUDs are used often as a communication tool between people from far apart places these commands are of quite high importance. All MUDs will have them. There are also often feeling commands. Feeling commands allow you to smile at people or flip them head over heals, or whatever. They exist to give the place more atmosphere, and allow you to put more feeling into what you say. Once you have figured out these basic commands you are ready to tackle the world.
Wander around exploring, trying to find some puzzle to solve, find something interesting to do. There is a large variety of things to do in a MUD. An old mud is often so large that you will never explore all of the parts of it. Many bits will remain hidden to you as you didn't read a description carefully enough and missed a secret passageway, or just not somewhere you wanted to explore.
MUDs are simple yet at the same time quite complicated. Underneath all of the commands you do lies a very complex system of parsing your commands and handling them correctly. Some MUDs are better at the command parsing than others. Discworld has one of the most advanced command parsing scheme's I have seen on any other MUD. It allows you to reference multiple objects and has quite a sophisticated error message and success message generation scheme.
Some of the things you can do on Discworld. You can go and play Live Eel Wrestling, go fishing and catch some fish, learn the somewhat dangerous art of Wizardry. Enter into the Netherworlds and never think the same way again. Get arrested by Carrot for fighting in a open space. Say eight and regret it. Send mail to someone via frogs, send someone flowers via the Womble delivery system. Explore the Unseen University, just don't say the M word to the librarian. Explore the world. Guaranteed not to look anything at all like the map which has now been published of Terry Pratchett's world. All of these things and many more are available now on Discworld. MUDs are fun and can be quite enlightening at some points.
Some Muds have www home pages setup. There are two examples below: