This is what is commonly known as a Rocket Stove. It is so efficient that with very little fuel the fire can get roaring like a rocket. My neighbor who has this stove as since learned she can use a lot less twigs. You can burn most anything in it and when camping there is abundant fuel lying about in the source of little sticks from trees.
Air feeds in from the holes at the bottom and the fuel sits on a tray inside.
My other neighbor has this stove which she found on eBay. I had never seen or heard of one like this before. It is made in Sweden for boats and sail boats. It burns alcohol which burns clean with no smoke or carbon monoxide.
It needs very little alcohol so a can last a long time. The alcohol sits in the middle port then you place the diffuser on the lower left over the flame after lighting it. The foil wrapped cap on the upper right is to cap off the reservoir of unused alcohol for next time. I think she said that part was missing when she bought it and so made her own cap from a plastic top wrapped with foil.
You can control the heat by controlling the size of the flame.
The top tray in position for cooking...
...and turned over to use the unit as a heater for your living space.
She can cook inside and heat the inside of her van with no worries or fumes.
Most of the time she cooks outside and the flame is protected from the wind.
And best of all the inner workings are mounted in a way that it swivels always being level, a necessity for boat life. That works great for on the road life too and I know for it is annoying to have your eggs slide over to one side of the pan all the time.