The "magic" cooker (thermos) is a cooking utensil which consists of 2 containers, one inner pot (for direct heating) and a vacuum cooker (for heat-preserved cooking). The cooker works the same as vacuum flask. The vacuum layer confines the heat absorbed by the food to the container. After a short boiling period, the food can automatically continue cooking itself using the heat preserved inside.
Due to shorter heating time used, less consumption of fuel during cooking, especially these days where gas and electricity cost is forbiddingly high. Since the food keeps cooking itself automatically using the heat accumulated inside, no need to pay constant attention over the food as in traditional cooking methods.
I have been using this pot nowadays to cook my soup and it helps me save on the cost of gas.