Infocom was a software company, that produced (strictly IMHO) the most excellent text adventures in the world.
The humor of the old Infocom Adventures is legendary: always unexpected, always far out, but unimaginably funny. This was aided by an incredibly advanced parser, combined with excellent scriptwriting, which gave unique responses for even the most far fetched entries possible. Try to "Kiss Door" in some games, the results will be hilarious. Other games required the same entries multiple times before yielding the desired results. However, the puzzles were mostly logical, and the games never unfair, although you could spend days figuring out how to solve some of them, and months on some games.
Another feature was the packaging, or rather what was inside it besides the manual and the game discs. Some games had comic books, some sow-on patches, some blueprints, and plain silly stuff, such as the contents of the Hitchhiker's Guide to the Galaxy game: Fluff, a miniature space fleet, a pair of don't panic shades and a button. Because of this, many fans insist on owning the original versions, which are notoriously hard to find these days, while the anthologies, which only collect the games themselves, are mostly shunned. Got for the games, but they don`t provide the full experience. Oh the days, when one could still buy them in stores. If I think about it, it was one of the best forms of copy protection ever, because it made you want to buy the game.
To find enjoyment in these games you should enjoy typing in short phrases and reading code, as there games did not provide any graphical details, everything was described in plain texts, which could be several pages long, and were usually very entertaining. That is why they were called Interactive Fiction. Many of today's gamers will probably just find them boring (and won't know what they are missing).
Here is a list of games Infocom produced:
I am aware that I might have forgotten a few games, but it has been a while. Note that I didn`t play them all, wish I had the time (or money to buy original editions instead of the anthologies)
Finally a link to more information to Infocom and their games, the best I've seen so far