What is Porter's five forces by Wiki

Porter's five forces is a framework for the industry analysis and business strategy development developed by Michael E. Porter of Harvard Business School in 1979. It draws upon Industrial Organization (IO) economics to derive five forces that determine the competitive intensity and therefore attractiveness of a market. Attractiveness in this context refers to the overall industry profitability. An "unattractive" industry is one in which the combination of these five forces acts to drive down overall profitability. A very unattractive industry would be one approaching "pure competition", in which available profits for all firms are driven down to zero.
Three of Porter's five forces refer to competition from external sources. The remainder are internal threats. It is useful to use Porter's five forces in conjunction with SWOT analysis (Strengths, Weaknesses, Opportunities, and Threats).
Porter referred to these forces as the micro environment, to contrast it with the more general term macro environment. They consist of those forces close to a company that affect its ability to serve its customers and make a profit. A change in any of the forces normally, requires a business unit to re-assess the marketplace given the overall change in industry information. The overall industry attractiveness does not imply that every firm in the industry will return the same profitability. Firms are able to apply their core competencies, business model or network to achieve a profit above the industry average. A clear example of this is the airline industry. As an industry, profitability is low and yet individual companies, by applying unique business models, have been able to make a return in excess of the industry average.
Porter's five forces include - three forces from 'horizontal' competition: threat of substitute products, the threat of established rivals, and the threat of new entrants; and two forces from 'vertical' competition: the bargaining power of suppliers and the bargaining power of customers.
This five forces analysis, is just one part of the complete Porter strategic models. The other elements are the value chain and the generic strategies.^{[citation needed}