An ETF (exchange-traded fund) is a type of passive investment product that typically tracks a basket of assets such as stocks, bonds or commodities. Just like ordinary shares, an ETF can be freely bought and sold on stock exchanges during trading hours. Most ETFs are index-based products, mimicking the composition and the performance of a specific gauge, such as the S&P 500 or the Hang Seng Index. The first ETF was launched in 1993 in the US.