What is AP and what can we do with AP?

AP are advancement points, you get them when you nurture egglings and hatchlings, 1 point for every 10 nurtures. You also get them when you fight in festival zones or missions that advance the storyline. There may be other ways to get them, but I can't think of any at the moment. You can spend them on your avatar to get things like hair styles, clothing and other things.