Chekhov's gun is a writing principle emphasizing that every element in a story should have a purpose, with a famous quote attributed to playwright Anton Chekhov stating, "If in the first act you have hung a pistol on the wall, then in the following one it should be fired". Introduced by Chekhov as advice to other writers, this principle means that any significant or prominent object, detail, or character trait should later play a crucial role in the plot or theme, avoiding unnecessary elements and false promises to the audience.