metaethics, which is about something or other that I can't quite figure out

Metaethics is about coping with people disagreeing about what is and is not awesome.

It happens after all. Some people think that copying art so that more people can experience it is awesome. Others think that it's so non-awesome that preventing the first group from doing it is awesome. Yet another group is indifferent to copying, but thinks the prevention is so non-awesome that preventing that is awesome. (This was the least mind-killing example I could think of. Please don't derail the discussion arguing it. The point is that there are nontrivial numbers of human beings in all three camps.)

We also observe that the vast majority of humans agree on some questions of awesomeness. Being part of a loving family: awesome! Killing everyone you meet whose height in millimeters is a prime number: not awesome! Maybe this is just an aspect of being human: sharing so much dna and history. Or maybe all these people are independently rediscovering some fundamental truth that no one can quite put their finger on, in much the same way that cultures around the world invented arithmetic long before Peano.

What can you do when you meet someone who disagrees with you and a lot is at stake? Well, there's always force. Or if you have some ideas about awesomeness in common, you can argue based on those. Is there another option? In practice, people do change their idea of awesomeness after talking to other people.

The "people" who disagree don't have to be separate beings. They can be subminds within a single human. The situation is pretty much the same (except you can't really use force).

Metaethics is that art of trying to deal with this. It hasn't gotten very far.