A mutual fund is a type of investment fund. An investment fund is a collection of investments, such as stocks, bonds or other funds. Unlike most other types of investment funds, mutual funds are “open-ended,” which means as more people invest, the fund issues new units or shares. A mutual fund typically focuses on specific types of investments. For example, a fund may invest mainly in government bonds, stocks from large companies or stocks from certain countries. Some funds may invest in a mix of stocks and bonds, or other mutual funds