Mutual funds issue units to investors in proportion to funds contributed, with the goal of providing better returns at minimum risk. There are two main types of mutual funds - open ended and close ended. Open ended funds offer continuous sale and repurchase of units at net asset value, while close ended funds specify a limited redemption period and only sell a set number of units during an offering period. Mutual funds also differ based on whether they focus on income, through regular dividend payouts, or growth, through capital appreciation and some dividend income.