My son wants to know what it "means" when the moon has a ring around it. I told him why it occurs?

Answer 1

If you're talking about a "halo", it means that rain is on the way. The light being reflected from the moon, are be refracted by the ice crystals in the atmosphere. I hope that helped you. Let me know if you need more than this.

Answer 2

High thin clouds, called cirro stratus clouds, containing ice crystals causes the rings around not only the moon, but the sun as well, this is caused by the crystals reflecting the light the same way rain drops reflect the sun light causing the rainbows. So the next time you see high thin clouds, that is going to cause a moon bow.