This is one of the lesser known heating methods, at least for most of the US. Essentially it acts as a large sauna heater, using large rocks placed on top to absorb and distribute heat throughout your space. The beauty is that the rocks get quite warm, but not nearly as hot as the stove. This makes it effective for warming up socks and boots, and even food. Also, should you need to leave, you can extinguish the fire and the stones will continue to provide heat throughout your cabin while not placing it at such a high risk of fire.
Here is nice basic how to on barrel stoves in the link below:
