Mutual funds are a managed portfolio of investments that pools money together with other investors to purchase a collection of stocks, bonds, or other securities, providing diversification. Learn about what mutual funds are and their advantages., What are mutual funds? A mutual fund is an SEC-registered open-end investment company that pools money from many investors. It invests the money in stocks, bonds, short-term money-market instruments, other securities or assets, or some combination of these investments., , , , .