Peter Lynch was an American investor who managed the Magellan Fund at Fidelity Investments from 1977 to 1990, delivering annualized returns of 29.2% and making it the best-performing mutual fund. His 4 key investing lessons were: 1) Invest in what you know through consumer experiences and fundamental analysis; 2) Be patient and don't get scared out of stocks during downturns; 3) Diversify across industries and companies with different earnings growth rates; 4) Do thorough research by turning over many rocks.