Seinfeld: "They're not really laughing at the joke, they're laughing at you."
What location is to real estate, delivery is to standup.
A cool extra scene from The Zen Diaries of Garry Shandling features Shandling, Jerry Seinfeld, and Chris Rock hanging in the green room. Jerry talks about the importance of delivery and how you can tell the exact same joke twice to wildly different reactions:
You get this reaction that's double. But it's the same idea. And then you realize they're not really laughing at the joke, they're laughing at you.