A mutual fund is a professionally-managed investment scheme, usually run by an asset management company that brings together a group of people and invests their money in stock, bonds and other security. Desecration: As an investor, you can buy mutual fund 'unit', which basically represent your share of holdings in a particular scheme. These units can be purchased or redeemed as needed at the fund's current net asset value (NAV). These NAVs Keep fluctuating according to the fund's holdings. So,each investors participates proportionally in the gain or loss of the fund.