Rogue is an old text mode computer game from 1980. It was the first role-playing game to use cursor addressing instead of just outputting text that scrolled off the top of the screen. Rogue inspired a whole genre of games called, not surprisingly, Roguelike games. The best known of them are NetHack and Angband.
Rogue Clone IV is an open-source reproduction of this classic game. It can be configured to look like either the UNIX or IBM PC versions of standard rogue.
If you feel like surfing, some good rogue web sites are Donnie Russell's home page, Nick Kisseberth's Roguelike Restoration Project, Glenn Wichman's Brief History of Rogue, Edwin Rots' Dungeons of Doom, and Björn Bergström's Roguelike Archive. You should also check out the rogue sections of the Wikipedia and the Open Directory.