Exchange traded funds (ETFs) are uniquely structured investment products that track indexes, or baskets of assets, including stocks, bonds, currencies, real estate and commodities. Because ETFs can cover a broad range of assets, they offer investors diversity from a single investment. When you purchase ETF shares, you are buying shares of a portfolio that tracks the yield and performance of its underlying asset(s). Like stocks, ETFs can be purchased on margin and sold short, and prices fluctuate throughout each trading session as shares are bought and sold on various exchanges.