Mutual funds belong to a group of financial intermediaries known as investment companies, which are in the business of collecting funds from investors and pooling them for the purpose of building a portfolio of securities according to stated objectives. They are also known as open-end investment companies. Other members of the group are closed-end investment companies (also known as closed-end funds) and unit investment trusts. In the United States, investment companies are regulated by the Securities and Exchange Commission under the Investment Company Act of 1940.

Mutual funds are generally organized as corporations or trusts, and, as such, they have a board of directors or trustees elected by the shareholders. Almost all aspects of their operations are externally managed. They engage a management company to manage the investment for a fee, generally based on a percentage of the fund's average net assets during the year. The management...