The document discusses the relationship between risk and return when investing. It states that there is a trade-off between expected risk and expected return, with higher risk investments typically offering higher returns to compensate investors for taking on more risk. It also discusses how diversification across multiple assets can reduce the non-systematic/diversifiable risk in a portfolio, but not the systematic/market risk that is related to movements in the overall market. The document defines beta as a measure of a stock's systematic risk relative to the market.