Mods (short for "modifications") are more than just user maps; they are user-made changes to how the game functions, such as alterations to the properties of enemies, how weapons behave, what the player can interact with, and a whole host of other possibilities. Mods often contain their own user maps that showcase changes to the game, but not all mods contain user maps.
Total conversions are a special class of mods that take this a step further. Rather than simply altering the game, total conversions change the game completely, often resulting in an entirely different game. It is sometimes ambiguous whether a mod should be considered a total conversion, but total conversions usually replace nearly all of the artistic and audio assets in the original game and may involve radical changes to core aspects of gameplay.
List of Duke Nukem 3D mods and total conversions
See Also: Category:Duke Nukem 3D mods