Uh, well there's four nations. The Earth Kingdom, which is where Ba Sing Se is; the Water Tribes, I'm from the southern one; the Fire Nation, who started the war; and the Air Nomads, who were wiped out. We're not as technologically as advanced as your world. We haven't discovered electricity yet and most things are powered by either steam, coal, or bending. The latter being a special elemental control that only certain people can do.

... that cover it?