nethack is a single user game based off of the game hack which itself was a clone of rogue. It has a very long history and continues to be developed to this day. The version of the AT&T 3B2 1000-70 is 3.x.
nethack uses VI keys plus many other commands. When in the game, type '?' to bring up the menu. From there you can get just about all the info you will need to play the game.
The object is to retrieve the Amulet of Yendor from the Dungeons of Doom and return with it, alive, to the surface.