Portfolios are simply combinations of different securities. The characteristics of investments do differ when we possess them in combinations or portfolios. As we shall see, an asset held as a part of a portfolio is normally less risky than the same asset held in isolation. Sometimes an asset which is highly risky when held in isolation may not be risky at all if it is held in a well diversified portfolio. How is it possible? Let us know reasons as well as the procedure to calculate the portfolio Risk and Return.