I am talking about IF.
A MUSH is a form of MUD, multi-user dungeon. I don't know what MUSH
stands for, but generally people on MUSHes talk to each other more
and people on MUDs kill each other more.
The presentation is like ordinary single-player interactive fiction,
but there are many other people on the MUSH for you to interact with.
Phil Goetz@cs.buffalo.edu