CAPM (Capital Asset Pricing Model)
The classic model for the return an asset should offer: the risk-free rate plus its beta times the market's risk premium. It says you're only rewarded for market risk you can't diversify away, not for risk you could have removed.
Where this is taught
Definitions are the trailer. These free levels turn CAPM into something you play — one bite-size lesson, with worked examples, a quiz and XP.