Adzes work in a similar way to chisels. When swung, the sharp-bladed head carves away slivers of wood.
Repeated swings carve away more and more material, allowing you to make a surface smooth, remove bark or hollow out a piece of wood.
Using an adze takes skill and practice. In Norway, carpenters sometimes compete to show off their skills by being the best at sharpening pencils using long-handled adzes. They turn the pencils around with their feet!