A sketch is a rapidly executed freehand drawing that is not usually intended as a finished work. A sketch may serve a number of purposes: it might record something that the artist sees, it might record or develop an idea or concept for later use or it might be used as a quick way of graphically demonstrating an image, idea or principle.
Sketches can be made in any drawing medium. The term is most often applied to graphic work executed in a dry medium such as silverpoint, graphite, pencil, charcoal or pastel. It may also apply to drawings executed in pen and ink, digital input such as a digital pen, ballpoint pen, marker pen, water colour and oil paint.

Sketching is a very important tool for a designer. Not only is it possible to make visual records of existing designs, but it is also useful to work out new design ideas. A sort of visual brainstorming, to consider first thoughts in greater depth and refine initial ideas.

Sketching is a powerful process to use because it always helps discover the best ideas and solutions to a design problem. It is a difficult task to ‘freestyle’ a complex design out of midair without hashing out the details. This is why sketching will remain an important step in the design and development process.