Proportion involves getting the sizes of objects correct relative to each other in a composition. The document discusses human proportions and provides examples from Leonardo Da Vinci's Vitruvian Man and Andrea Mantegna's Dead Christ. It also defines foreshortening as rendering an object or figure in depth to show distortions in perspective. Observing proportions in these examples and using techniques like measuring with a pencil, using a viewfinder to divide space into a grid, and focusing on basic shapes can help one accurately draw objects and figures, especially those seen at unusual angles or from a distance.