The SPY ETF, or SPDR S&P 500 ETF Trust, is an exchange-traded fund that aims to track the performance of the S&P 500 index. This index includes 500 of the largest publicly traded companies in the United States, representing a broad cross-section of the economy. Investors buy shares of the SPY ETF to gain exposure to these companies without having to purchase individual stocks. Launched in 1993, the SPY ETF is one of the most popular and widely traded ETFs in the world. It offers investors a way to diversify their portfolios while benefiting from the overall growth of the U.S. stock market. The fund is known for its liquidity and relatively low expense ratio, making it an attractive option for both individual and institutional investors.