The feature they all have in common is that all of them are used by moving the pointer across the image display, creating brush-strokes. 

(i ) Four of them 

• the Pencil, 
• the Paintbrush, 
• the Airbrush and 
• the Ink tool 

behave like the intuitive notion of “painting” with a brush. Pencil, Paintbrush, and Airbrush are called “basic painting tools” or brush tools. 

(ii) The other tools use a brush to modify an image in some way rather than paint on it: 

• the Bucket Fill fills with color or pattern; 
• the Gradient fills with gradients; 
• the Eraser erases; 
• the Clone tool copies from a pattern, or image; 
• the Perspective Clone tool copies into a changed perspective; 
• the Heal tool corrects small defects; 
• the Convolve tool blurs or sharpens; 
• the Smudge tool smears; 
• and the Dodge /Burn tool lightens or darkens. The advantages of using GIMP with a tablet instead of a mouse probably show up more clearly for brush tools. These tools also have special “Pressure sensitivity” options that are only usable with a tablet.