By TheStreet Staff What Is a Mutual Fund? A mutual fund is essentially a professionally managed portfolio of stocks and/or other securities funded with a pool of capital sourced from many individual investors. Each investor receives gains, interest payments, and/or dividends proportional to the amount of capital they have invested in the fund. Mutual funds are popular because they allow investors to buy into a carefully curated and well-diversified basket of securities put together by a professional investor or team of investors with a particular goal or objective in mind. Every mutual fund ha…