A sovereign wealth fund is money that a country saves. Instead of spending all the money on things like roads and bridges, countries like China and Qatar put some of their money away in a special fund - like a big piggy bank. We call this a sovereign wealth fund. They keep the money there and use the money to buy things that can help their country, like stocks and bonds in other countries. That way, they can invest in other countries and even earn money if those countries do well.