I am! From what I understand, what you call the Human Realm would be called the Material Plane for us. There are also Elemental Planes and the Feywild, which we can access if we know where an entrance to them is. My people, the Air Ashari, guard the Elemental Plane of Air to make sure nothing terrible slips through, as the portal can be unstable at times. The Abyss is another Plane, but it's far less accessible as there was a Divine Gate created to keep both the Gods and the terrible creatures of the Abyss from slipping through, yet that hasn't stopped them from picking a fight with us.
Well, the natural world would be drawing power from the earth, the sky, the water, and fire. From beasts and flora. I guess supernatural would just be everything outside of that. Arcane energy, I'm not sure anyone knows how it works, just that it's there.