When I started my account on aviation stack exchange I was already signed up for aviation meta, but what questions do I ask on this website and what is it for?
Meta is for questions or discussion about the Aviation SE site itself. Questions can be about what is on topic, how things work on the site, or possible improvement, etc. All SE sites have a meta (or at least all the ones I use). I presume the reason that the Aviation SE automatically signs you up for meta is because the site is still in beta.