A dungeon represents one of the possible areas where a roguelike game is played. Dungeons are subterranean mazes of rooms interconnected by corridors and stairways, where each level is progressively more dangerous and has greater rewards. Note that this is a description of standard dungeon layout for play. Rooms might be replaced with natural caverns and stairways by chutes and ladders. The progressive nature is a necessity of gameplay.
There are some hardcore roguelikes in which all or most of the action happens inside a dungeon, thus increasing the “Dungeon-Hack” factor.
The first roguelikes were centered around dungeons, which were first represented as rectangular rooms joined with passageways, and had a horizontal division of levels, connected by ascending and descending stairways.
In some other games, there is a wilderness or some other kind of overworld, from which you can get to different dungeons.
Dungeons are the oldest class of roguelike maps, and are favored for their easy generation and clearly defined “levels”; they are present in almost every roguelike, either as the main action stage or as complementary areas.
The nature of dungeons as playgrounds full of monsters and treasure that increase in reward as the game advances, has spawned a subgenre of CRPG that is known as dungeon hacks, in which the storyline is not very important, and which are pure tactical gaming. Most roguelikes, including some of the big ones, may be described as dungeon hacks. Some games utilize alternatives as a complementary feature to the dungeon hack. For example ZAngband has large wilderness area and Xenocide has some city sectors to explore. Caves are also quite common in games. These can be found in ADOM, DoomRL, ZapM and others.
In real life, a dungeon is a prison cell or set of cells inside a castle or fortress. The word originally comes from the French “donjon”, the central keep usually used as a last defensive stand or to keep prisoners. The current gamer’s usage as an underground adventuring area is from Dungeons & Dragons.