The capital asset pricing model, or CAPM, is a financial model that calculates the expected rate of return for an asset or investment.
CAPM does this by using the expected return on both the market and a risk-free asset, and the asset’s correlation or sensitivity to the market (beta).
There are some limitations to the CAPM, such as making unrealistic assumptions and relying on a linear interpretation of risk vs. return.
Despite its issues, the CAPM formula is still widely used because it is simple and allows for easy comparisons of investment alternatives.
For instance, it is used in conjunction with modern portfolio theory (MPT) to understand portfolio risk and expected return.
Source: Investopedia.