My take-aways so far:
1. AG is set on a far future Earth, not some other planet. Earth has an unusually large moon for its mass, and we wouldn't expect another planet to have such a large satellite. Plus the moon as pictured looks very much like our own moon.
2. The AG Earth civilization has achieved sustainability, at the cost of becoming a rural backwater. It's not without technology (remember the giant windmill Alice was on at the beginning? That suggests electrification), but there's no large-scale industrialization. The windmill may be a leftover that the current Earth population would not be able to replicate. Earth has a "scarcity-based economy" that uses money, which is anachronistic in the larger context.
3. Earth's status is protected by the surrounding Praeses civilization, which is probably interstellar in scope. It has progressed beyond scarcity, and does not use money.
4. The Praeses are AI's, and the civilization they run is similar to the Culture, with humans no longer in charge of anything. Humans are the wards of the all-knowing AI's, the Praeses. Ardent and Gavia should not be seen as representative members of the society, however. They're just children.
5. Earth is run as a kind of nature preserve, in which humans live anachronistically. When AI's took over from humans, the AI's decided to keep the Earth as a kind of historical monument. Its biosphere and humans were kept in a semblance of its earlier natural state. The natural state isn't all that accurate a depiction of earlier times, just as the Yellowstone Park you see now is not the same as the natural wilderness from which it was made.
6. Alice is an agent of the Praeses civilization, and she is tasked with keeping the anachronistic Earth society running smoothly. Alice ultimately reports to the Praeses. I'm doubtful she's an android (though she might be); her function is like a park ranger.
7. Ardent and Gavia (beyond their narrative function as audience stand-ins) were allowed into the usually protected Earth nature preserve for some purpose. Alice knows this, but she does not know any more than we do what that purpose is. The purpose may be large (something to do with the Praeses civilization as a whole) or it may be about them personally (see Spirited Away for something similar).