The article discusses how the returns of investments are important for building portfolios and evaluating performance. It explains different ways to calculate investment returns, such as periodic and average returns. The performance of an investment can be assessed using the geometric mean return, while the performance of an investor is evaluated using the money-weighted return. Asset returns can be broken down into nominal and real components. The expected return includes a risk-free interest rate and a risk premium, which can be estimated using historical returns or scenario analysis.