Along with salt peter (potassium nitrate) and sulphur, ground charcoal is one of the ingredients in making Black Powder. Generally the proportions of the ingredients are 75% salt petre, 15% Charcoal powder and 10% sulphur. Each component is ground separately before they are all mixed together to form black powder.
The name Black Powder brings to mind explosives and gunpowder, but it was first used to make fireworks long before the invention of firearms.
In both firework making and gun powder manufacturing the charcoal provides lift and acts as a propellant. Willow charcoal is a particularly good propellant and lifting agent. These qualities arise from the fact that willow grows so quickly and is such a soft wood. It is the softest woods that provide the greatest lift.