I think we really need an American to answer this one. Popcorn is simply dried grains of what is called corn in US and maize in GB. When it is heated, the water inside the grain turn to steam, the grain turns inside out and looks fluffy and white. It is often sold as a snack in cinemas, etc.
The usual way of cooking popcorn is to subject it to high heat in a lidded container (otherwise it will be all over the kitchen!) and cook it with butter or oil.
Air-heated popcorn uses no fats in the cooking. I don't know the process, but I wonder whether a "popcorn maker" (kitchen gadget) would allow this.
Pop corn looks and tastes a bit like lumpy cotton wool.
Here is a picture of pop corn.
http://www.popcornpapa.com/