"To understand supply chain management, one must first begin with a discussion of a supply chain; a generic one is shown. The supply chain shown in the figure starts with firms extracting raw materials from the earth -- such as iron, oil, wood, and food items -- and then selling these to raw material suppliers such as lumber companies, steell mills, and raw food distributors. These firms, acting on purchase orders and specifications they have received from componenent manufacturers, turn the raw materials into materials that are usable by these customers (materials such as sheet steel, aluminum, copper, lumber, and inspected foodstuffs.) The component manufacturers, responding to orders and specifications from their customers (the final product manufacturers) make and sell intermediate components (electric wire, fabrics, plumbing items, nuts and bolts, molded plastic components, component parts and assemblies, and processed foods). The final product manufacturers (companies such as Boeing, General Motors, and Coca-Cola) assemble the finished products and sell them to wholesalers or distributors, who then resell these products to retailers as their product orders are received. Retailers in turn sell these products to us, the end-product consumers."