From the introduction:
Remnant, a world where people wield the light of their souls, Aura, and nature's wrath given form, Dust, to fight back against the encroaching darkness of the soulless Grimm, twisted monsters resembling bone covered animals. Four Kingdoms stand strong, points of light against the night, but so very easily snuffed out should the forces of destruction overwhelm them. Human and Faunus live in a world, broken and beautiful, yet so torn by danger from without and from within. You enter a year before the events of RWBY Season 1.