A Mutual Investment Fund (MIF) is a consolidation of funds transferred by individuals and legal entities to a management company for trust management, in order to receive profit on the assets consolidated into the fund, and to distribute the received profit among the investors (unit holders) in proportion to the number of units held.

Investment Unit (unit) — a registered security certifying the right of its owner to a part of the fund's assets, as well as to the redemption (repayment) of the owned unit in accordance with the rules of the fund. Thus, investment units certify the investor's share in the fund’s assets and the investor's right to receive money from the mutual investment fund corresponding to this share, that is, to redeem the units at the current price. Each investment unit provides its owner with the same scope of rights. Records for the rights of the holders of investment units (the Register) are maintained by an independent organisation providing maintenance of this register of the investment unit holders.
Units may be pledged, given, inherited and sold at almost any time.

The MIF’s assets may be securities (shares, bonds, mortgage securities, units of other funds, etc.), real estate, etc.

A special financial organisation — the asset management company (AMC) — manages the MIF's assets. It decides which securities or other assets to buy, and when to buy or sell them.