The document discusses visualisation diagrams, which are drawings created by hand or digitally to plan and show what a final product or design will look like. Visualisation diagrams are used to plan things like costumes, logos, posters, cars, and webpage layouts. The purpose of visualisation diagrams is to plan designs and layouts before creating the final product or image. The document provides examples of visualisation diagrams and tasks for students to create their own diagrams to demonstrate understanding of their purpose and construction.