Looks like the remains of a log torch - if I remember correctly one drills down the middle of a log about 80% of the way then drills a hole in the front of the log about 20% up from the ground to meet the other vertical hole. Then stuff some light kindling (like straw) into the back of the lower hole and light it, if you've got it right then the convection effect makes the middle of the vertical hole burn very brightly indeed.
you can make small versions for cooking with your billy can too, just take a small log about 3-4" accross and about a foot long.
user your hand axe or knife and rock (agh! my fallkniven!) to split it in half lengthways, then each section in half again, plant in the ground together leaving enough room to fill with kindling then light and pop your billy on top of the log. perfect little cooking stand all sorted for you.