The Charcoal tool simulates drawing with charcoal.
To use this tool...
After selecting the colours you want to draw with, click on the Charcoal button and point the cursor where you wish to begin drawing. Hold down the left mouse button to draw with the foreground colour; hold down the right mouse button to draw with the background colour. Move the mouse to begin drawing with the charcoal. The size of the charcoal can be changed by double-clicking on the Charcoal button.