Metaethics is the study of the nature of ethical properties and statements. It includes questions about the sort of evidence which can be used to support moral ideas, whether morality is culturally relative, and what the nature of moral facts could be.
Two major positions in metaethics are moral realism and moral antirealism. Moral realism has a number of forms, including:
Moral naturalism: The claim that moral truths are reducible to natural facts in the world.