In the early 90s there was an on-line role-playing phenomenon called DuneMUSH. Created on the PennMUSH base of code, it was a text role playing environment. Much of the basic setup was like the early text adventure game Colossal Caves / Adventure and Zork, where the player walked around in a text universe.
A player would type in a command such as "north". A player would then "move" to the next room in the north and the computer would describe it to you. He or she could interact with objects - "turn on lamp" or "pick up key". The best part of DuneMUSH is that it wasn't just a single person wandering through this world that was based on Frank Herbert's series. It was an entire group of up to 100 or more people on-line at any given point in time - all interacting, role playing, plotting, scheming.
Unlike modern MMORPGs where the aim is on gaining experience and slaying monsters, there was no health or combat or experience points in DuneMUSH, though the MUSH did have a rarely-used combat feature for player duels. The game was focused primarily on role playing. After logging in, a player would be recruited and trained by the heads of various guilds or factions available in the world.
One of the beautiful things about DuneMUSH was that every person playing was committed to the world and to role playing. There wasn't a lot of random chit chat about the weather or about 'real life' things (except in a special area called the hottub). When you were in the game, you were in character, and you reacted to other characters and worked on plots in character. It could literally run 24 hours a day, as various characters came and went and wanted to discuss plans.
Another great aspect was that each person could 'add to' the world. Some players could create new rooms in the house, decorate them, add code to hold banquets or parties or training lessons or even oversee duels. Each character could fully customize their appearance, could create gifts to give each other, could grow the universe, item by item. In this way, the world of DuneMUSH had a life of its own.