The Seven Peoples of the Earth are the seven identifying types applied to every sentient creature in the world.
The Seven Peoples of the World divided themselves in this manner (or were divided) somewhere around the First War, which covered the whole planet.
The symbology for the Seven Peoples has, over time, been roughly codified into seven distinct symbols:
The shorthand for these symbols (because who wants to spend the time to sketch all that out) is as follows:
A young (and smart-alec) Fey prince has his own opinions of the whole thing right here, if you’re interested in a short story.