The three main purposes of a section view are to document the design and manufacture of single parts, to document how multiple parts are assembled, and to aid in visualizing the internal workings of a design. The document then defines and provides examples of different types of section views such as broken-out sections, aligned sections, full sections, removed sections, revolved sections, and half sections. It also shows different hatch patterns used to indicate materials like cast iron, zinc, copper, steel, magnesium, and rubber in section views.