What are product requirements?
Product requirements describe what a product must do and the limits it must work within.
They cover behavior, important edge cases and what success looks like without dictating the implementation. Good requirements say what must be true and make clear which decisions are still open.
They aren't a design or technical plan. Those follow from the requirements.
Why it matters for product builders
Requirements are where you resolve ambiguity cheaply. Anything left vague is usually decided mid-build by whoever is closest to the work.