The world of finance revolves around two fundamental concepts: risk and return. When we invest, the goal is often to maximize return, minimize risk, or reach an optimal trade-off between the two. However, a higher level of risk often accompanies higher potential returns, and these two quantities are often positively correlated. For example, the previous chapter introduced low-risk and high-risk products, which also correspond to (relatively stable) low-return and (likely volatile) high-return assets. This risk manifests itself in the uncertainty of the investment outcome, meaning that we are not certain about whether the investment will be profitable or not, and, if profitable, how much. Thus, a risk-averse investor tends to prefer low-risk products that deliver more or less guaranteed returns.