A supply chain is the full network of organizations, people, and processes involved in moving a product from raw material to the final customer — including suppliers, manufacturers, warehouses, distributors, and retailers. 'Upstream' activities refer to everything happening before a product reaches a manufacturer (like sourcing raw materials), while 'downstream' activities cover everything after manufacturing, including distribution and retail. Supply chain management is the coordination of these moving parts to minimize cost and delay while maximizing reliability, because a disruption at any single link — a delayed shipment, a stockout, a quality issue — can ripple through the entire chain and directly affect whether a customer gets their product on time. Strong supply chain management is increasingly recognized as a major competitive advantage, not just a background operational function.