For old investors and those who are starting out, mutual funds are a wonderful and convenient way to invest your money. Simply put, a mutual fund is a collection of stocks (equities) and/or bonds (debt). When you buy shares (units) of a fund, you buy a very small proportion of that collection of stock and bonds. Instead of deciding which stock or bond to buy, you just give your money over to a Mutual Fund manager who takes it and decides on which stocks or bond to invest in for you.