Porter's Five Forces model is used to analyze the competitive environment in an industry and determine its profitability. The five forces are: 1) threat of new entrants, 2) bargaining power of suppliers, 3) threat of substitutes, 4) rivalry among existing competitors, and 5) bargaining power of customers. The model helps firms understand the industry structure and develop corporate strategies accordingly. For example, in the auto industry, there are many substitute options for sedans which increases the threat of substitutes. Suppliers also have strong bargaining power which affects industry profitability.