What is an ETF? By: MarketWatch October 09, 2019 at 15:49 PM EDT Exchange-traded funds are a great tool for investors, but there are some basics to understand about their benefits, like lower costs, and a few drawbacks. Read More >> Related Stocks: S&P 500 ETF Vanguard S&P 500 EW Invesco ETF S&P 500 Ishares Core ETF SPDR S&P 500 ETF Trust