MUD

A MUD (acronym for Multi-User Dungeon) is an online role-playing game that is usually text-based and accessable through telnet, as well as a variety of MUD clients.

Each MUD has its own sets of rules and policies. Some MUDs allow players to be out of character (OOC) as much as they like, while others require them to be in character (IC) more often, or always. Rules can vary in different areas of the MUD.

Unlike MOOs, MUDs are static environments that may contain objects that have descriptions and limited actions. While more advanced text-based environments allow for complicated object-heirarchy models to create a feature-rich world, MUD's are more akin to chatrooms that have describable objects.

While more chatty mediums such as IRC are more prone to idle users and periods of non-activity, MUD's typically disconnect idle users, so the ability to find partners for role-play are greater on a MUD or MUCK.

TinyMUD
TinyMUD was created by James Aspnes in mid-to-late 1989 and is the name of both an implementation of the MUD software, and the name of a MUD itself. TinyMUD, it's descendants and look-a-likes became the most popular software for social rather than role-playing (really MMORPG combat) MUDs. This includes virtually all furry themed MU*s.

TinyMUD quickly forked into three main groups:
 * TinyMUCKs - Most notable for their Forth-like programming language MUF.
 * TinyMUSH - Made popular by Pern fandom, it later came to have it's own MUSH code.
 * MOO - An object oriented variant of the server most notably used by LambdaMOO.

History
The first mud was created by Roy Trubshaw and Richard Bartle at Essex University in 1979. The original version merely allowed a user (player) to move about in a virtual location, later versions provided for more variation including objects and commands which could be modified on or offline. The goal for developing the first MUD was to test a newly developed shared memory system, the gaming aspect came later.