A sketchbook is a book or pad with blank pages for sketching and is frequently used by artists for drawing or painting as a part of their creative process. There are, perhaps, two broad categories for classifying sketches:

Observation: this focuses on the documentation of the external world and includes many such travel and nature studies.

Invention: this follows the artists' digressions and internal journeys as they develop compositional ideas.

Sketchbooks come in a wide variety of shapes and sizes, with varied covers, and differing numbers of pages. Sketchbooks began as a way to provide a readily available supply of drawing paper in the convenient form of a book. Finish of the work found in the sketchbook varies widely from artist to artist, with some having very simple drawings and lots of notes, and some having highly worked images.

PAFA has a small collection of artists sketchbooks that have been digitized and made freely accessible online.