MUD stands for Multi-User Dungeon, Multi-User Domain, or Multi-User Dimension. Regardless of what it stands for, a MUD is an online environment where multiple users are logged on and interacting with one and other. On some MUDs you only interact with other players that are logged on, similar to an online chat system. On other MUDs you can also interact with a game world where you can explore, fight monsters, and collect treasure, either alone or in the company of other players that are logged on. On some MUDs, the environment itself can be changed and expanded by the players themselves. On others, you must play the game long enough to advance to a Wizard level at which time you can add new areas to the game. Allowing players to change and add to the MUD world itself is one of the unique features that make MUDs so unique and fun. Every MUD you visit will be different in subtle or dramatic ways.
MUDs have been around since the early beginnings of the Internet. The first MUD was written by Roy Trubshaw and Richard Bartle at Essex University in 1979 on a DECsystem-10. For more information about the history of MUDs, take a look at The MUDdex (http://www.apocalypse.org/pub/u/lpb/muddex/) created by Lauren P. Burka.
For more information about MUDs, visit the incredible MUD Connector (http://www.mudconnector.com). This site has a detailed list of most every MUD on the Internet, along with every else you ever wanted to know about MUDs.
zMUD uses the MUD listing from the MUD connector as the database for its internal MUD Connection Wizard. You can select MUDs and view their description. zMUD also allows you to search the MUD list for various keywords. The entire MUD list can be quickly updated with records added or changed since your last update.