The punchline is the last few words of a joke — or sometimes of a story — that make people laugh or sit up. Everything before it sets the scene; the punchline is the hit at the end. If you give it too early, the joke dies. People also stretch it: “What’s the punchline?” can mean “So what is the real point?” when someone has been talking around an idea. It is everyday English, not fancy. You will see it written punchline (one word) or punch line (two words); both are used.

笑點（年輕人也說「梗」；笑話或故事最後那句）