Wikipedia's main navigation subsystems (overviews, outlines, lists, portals, glossaries, categories, and indices) are each divided into the following subject classifications:

• Reference works – compendiums of information, usually of a specific type, compiled in a book for ease of reference. That is, the information is intended to be quickly found when needed.

• Culture – encompasses the social behavior and norms found in human societies, as well as the knowledge, beliefs, arts, laws, customs, capabilities and habits of the individuals in these groups.