Porter's Five Forces model is used to analyze industry competition and attractiveness. The five forces include threat of new entrants, bargaining power of suppliers and buyers, threat of substitute products, and rivalry among existing competitors. The model helps understand an industry's structure and profitability. It is a useful tool for competitive analysis at the industry level and providing input for SWOT analysis. Some limitations are that it ignores internal strategy and does not account for synergies within large corporations.