That's why the price of a mutual fund share is referred to as the net asset value (NAV) per share, sometimes expressed as NAVPS. A fund's NAV is derived by dividing the total value of the securities in the portfolio by the total amount of shares outstanding. Outstanding shares are those held by all shareholders, institutional investors, and company officers or insiders. Mutual fund shares can typically be purchased or redeemed as needed at the fund's current NAV, which—unlike a stock price—doesn't fluctuate during market hours, but is settled at the end of each trading day.

The average mutual fund holds hundreds of different securities, which means mutual fund shareholders gain important diversification at a low price. Consider an investor who buys only Google stock before the company has a bad quarter. He stands to lose a great deal of value because all of his dollars are tied to one company. On the other hand, a different investor may buy shares of a mutual fund that happens to own some Google stock. When Google has a bad quarter, she only loses a fraction as much because Google is just a small part of the fund's portfolio.

• A mutual fund is a type of investment vehicle consisting of a portfolio of stocks, bonds or other securities. 
• Mutual funds give small or individual investors access to diversified, professionally managed portfolios at a low price.
• Mutual funds are divided into several kinds of categories, representing the kinds of securities they invest in, their investment objectives, and the type of returns they seek.
• Mutual funds charge annual fees (called expense ratios) and, in some cases, commissions, which can affect their overall returns.
• The overwhelming majority of money in employer-sponsored retirement plans goes into mutual funds.