What is Porters Five Forces, and why is it good to analyse industry & sector?

Porters Five Forces is a model that helps determine an industry's various forces, sources of power, and conditions of competition. This will inform strategy. 5-Force analysis helps managers figure out factors of competition, competitor or supplier power, and attractiveness of an industry through the following 5 things: 1. Suppliers (What is bargaining power of suppliers?) 2. New entrants (Are new entrants a threat?) 3. Buyers (What is the bargaining power of buyers?) 4. Substitutes (What is the threat of substitutes?) 5. How is competition between current actors on market?