This article or section contains lore taken from the Warcraft RPG books, and thus is not necessarily canon.
An NPC class is a class held by a non player character. Most characters are not heroes. They do not spend their days battling monsters, searching for magic items, or blasting their enemies with spells; they plow farms, make shoes, and sell rope. Some are artisans, some are grand or petty nobles; but whatever the case, they do not possess heroic classes like arcanist or warrior. Instead, they have other classes. Some characters, particularly those who oppose or ally with heroes, are suitably villainous or heroic to warrant the use of the base classes. These are the classes for those who do not spend a lot of time adventuring.WoWRPG 365
Dungeons & Dragons: Warcraft: The Roleplaying Game
Note: All of the NPC classes detailed in the Dungeon Master's Guide exist in the world of Warcraft.WRPG 54 However the actual articles for these classes can only be found in the Dungeon Master's Guide.