Global indices are statistical measures that track the performance of a specific group of stocks or other financial assets across different countries. They provide investors with a snapshot of market trends and economic health. Common examples include the S&P 500, which represents 500 of the largest U.S. companies, and the FTSE 100, which includes the top 100 companies listed on the London Stock Exchange. These indices are essential for investors as they help gauge market performance and make informed decisions. They can also serve as benchmarks for mutual funds and other investment portfolios, allowing comparisons of returns against the broader market.