"Chekhov's Gun" is the idea that if you write a gun into a story, that gun has to be fired. It refers to Anton Chekhov's firm belief that stories should contain exactly what they need to. No more.
When a story closes the loop on every single loop opened, that satisfies me deeply.
When we track and close the open loops in conversation together, that satisfies me deeply.
When the conversation contains exactly what it needs to and no more: We are having a Chekhov conversation.