A mutual fund is a pool of money used to invest in whatever the fund specializes.
Most funds specialize in stocks but some buy gold, bonds or other investments.
Many funds focus on certain areas like China or US technology stocks. Thousands of investors have put money into the fund which, in turn, invests the money in US stocks, the fund's specialty. A large full time staff monitors the investments and makes decisions under the direction of a fund manager. One appeal of mutual funds is that smaller investors receive the same world class expertise and purchasing power as the large institutions. Investors who buy funds need only be concerned with the quality and long term performance of the fund.