Put-Call Parity
A no-arbitrage identity tying a call, a put, the stock and a bond into one equation: hold the right combination and two portfolios must cost the same. Break it and there's free money, so it pins down how calls and puts are priced relative to each other.
Where this is taught
Definitions are the trailer. These free levels turn Put-Call Parity into something you play — one bite-size lesson, with worked examples, a quiz and XP.