Basically, a rocket stove is an insulated fire that burns efficiently and hot, releasing very little smoke or particulate matter and uses minimal amounts of small wood fuel. It's a fire that burns clean and runs on twigs. They come in all shapes and sizes and some are adapted as thermal mass heaters to heat homes.
The version that the ADG built comes from Root Simple's design, using a 5 gallon metal bucket, which I just happened to have on hand.
haybox cooker, for some majorly low-energy, fossil fuel free cooking!