Procedural Generation is the “random” process that the Diablo series uses to create most of its playable universe. It refers to the generation of content algorithmically rather than manually; or rather “on the fly” as opposed to before releasing the game. It is most apparent in level design, but can also apply to the generation of items, monsters, and quests. Procedural Generation adds replay value because each new game aims to be a different and unpredictable experience.
Map Generation is one of the defining features of the Diablo series and the most apparent difference to players every time a new game is played. It is the algorithm-based process by which areas of the game are created “on the fly”. Map Generation can have a profound impact on game play experience because it provides a basis for the other important aspects such as monster generation, loot, object placement, and even quests.