An example of a real-world PRD in action: https://github.com/yournextstore/new.store/blob/main/docs/new-store-prd.md
NOTE: That PRD is deeply thorough and far more comprehensive than your typical PRD; it's been optimized for vibe coding where LLMs are like junior, chaotic engineers that require a lot of detail and handholding to yield good results.