MUD stands for "Multi-User Dungeon", and refers to a text-based multi-user game centered around a fantasy adventure genre such as Dungeons and Dragons.
In a typical MUD, a person would connect to a MUD Server using a Telnet client (such as windows Telnet) or a MUD client (which is usually just a fancy telnet program).
That person would then create a character. A character is an adventuring person whose role you would take on whenever you log into the MUD. A character may be a sword swinging Fighter, a sneaky Thief, a spell casting Mage, a powerful Cleric, or even a singing Bard. Your character can also be of many different races, including Elf, Gnome, Dwarf, Human, Halfling, and sometimes many others.
Once a person has a character in a MUD, they may take that character on wondrous adventures. A character may explore vast caverns, fight numerous monsters, uncover fabulous treasures, solve intriguing puzzles, and avoid numerous traps.
The object, however, is always the same: to advance the character in Experience. As a character advances in Experience, he or she also gains new powers and capabilities, allowing the character to take on even more difficult monsters and explore more dangerous places, with even greater reward.
A Mud is Text Based
In this world of computer games with amazing graphical capabilities, why would anyone play a text based game? Another question might be: If we have television, why bother reading books? The answer is the same. Our imagination still provides greater inspiration than any high resolution computer game, or any television show can mimic.
MUDs can be extremely well written at times, providing descriptive places and monsters that interact with you at a level of complexity unmatched in the best computer game. Also, since your interaction is through english word commands, your ability to interact with the world is also greatly enhanced. In fact, interaction can be so complex and realistic that many people play MUDs just for that social interaction, foregoing the greater aim of advancing a character.
In conclusion, it should be pointed out that a MUD can be the most addictive, rewarding leisure experience of your life, if you give it a chance. There are also numerous web sites and hundreds if not thousands of MUDs to play, each with their own special characteristics and twists to enhance the experience for all concerned.