From the introduction:
They set out to make something from nothing. It’s not clear whether they succeeded or not. See, it turns out there’s a lot of grey area between something and nothing.
You’re alive, but you’re not real. You don’t have a soul. You don’t have childhood memories, because you don’t have a childhood. You don’t have parents; you have makers. And those makers forgot to give you a place in the world.
This is a playbook or "skin" (character sheet and basic play rules) for the Hollow character.