Brush pens can be used to change the thickness of the stroke when writing by varying the pressure. This creates the characteristic brush lettering script.
You can also use a brush pen to colour large areas, which can be coloured much faster.
The special feature of brush pens is their flexible brush tip. By varying the pressure, they can be used to change the width of the stroke when writing, drawing or painting. A lot of pressure results in broad strokes and a lot of colour. Little pressure, on the other hand, results in thin lines and little colour on the paper.