The Setting namespace describes the In Character game world. As a player, you can create your character here, and as storyteller you can describe everything about the world, including non-player characters, locations like major cities or landmarks, macguffins, factions, in-character religions and deities and anything else that you feel is important.
In general, we advise creating a page for each entity you describe, so one page per non-player character, one page per location, etc.