MUDs + MOOs

MUDS & MOOs are a form of communcative devices.
A MUD (Multiple User Dimension) is a computer program which users can log into and explore. Each user takes control of a computerized persona / avatar / incarnation / character. You can walk around, chat with other characters, solve puzzles, and create your very own rooms, descriptions and items. MUDs are usually more social in orientation. The players on these types of MUDs tend to chat, meet friends, make jokes, and discuss various topics.

MOOsMOO is an acronym for Multi-user-dungeon Object Oriented. MOOs are fully interactive societies in which you can role play, or project your real self, as you wish. Its most common use is as a multi-participant, virtual reality adventure game with players from all over the world. You can interact with the people there, but you can also build a home, create pets and other objects, and code / program new items.