What is SPDR S&P 500 ETF (SPY ETF)?

The SPDR S&P 500 Trust ETF, sometimes called the SPY ETF, is one the most well-known electronically traded funds (ETFs) in the world and currently trades on the New York Stock Exchange (NYSE). The SPY ETF is used to track the American Standard and Poor's 500 Index, or S&P 500, which is composed of 500 of the largest companies listed on the U.S. stock market and many of the largest tech stocks on the planet including Apple Inc., Microsoft, Amazon.com, Facebook, Alphabet Inc. (class A & C), Tesla Inc., and Berkshire Hathaway.