Metaethics is the attempt to understand the metaphysical, epistemological, semantic, and psychological, presuppositions and commitments of moral thought, talk, and practice. As such, it counts within its domain a broad range of questions and puzzles, including: Is morality more a matter of taste than truth? Are moral standards culturally relative? Are there moral facts? If there are moral facts, what is their origin? How is it that they set an appropriate standard for our behavior? How might moral facts be related to other facts (about psychology, happiness, human conventions…)? And how do we learn about the moral facts, if there are any?

These questions lead naturally to puzzles about the meaning of moral claims as well as about moral truth and the justification of our moral commitments. Metaethics explores as well the connection between values, reasons for action, and human motivation, asking how it is that moral standards might provide us with reasons to do or refrain from doing as it demands, and it addresses many of the issues commonly bound up with the nature of freedom and its significance (or not) for moral responsibility.

(Via Stanford Encyclopedia of Philosophy)