An ETF, or exchange-traded fund, is a marketable security that trades like a stock. ETFs can track an index, a commodity, bonds, or a basket of assets like an index fund. ETFs are unlike mutual funds. ETFs experience price changes throughout the day as they are bought and sold. ETFs typically have higher daily liquidity and lower fees than mutual fund shares, making them an attractive alternative for investors. Because it trades like a stock, an ETF does not have its net asset value (NAV) calculated once at the end of every day.