Interactive fiction is another name for text adventure games. If you don't know what those are, but are curious, here is a good introduction. This is not a current interest of mine, but once I was involved enough to write a game, Erehwon, that placed a not-very-impressive 11th in the 1999 Interactive Fiction Competition. (It's not related to the novel of almost the same name by Samuel Butler.) Below are some links related to the game.
To play the game, you need a TADS interpreter, which you can get from the IF archive.