Anton Chekhov was a Russian author, often considered a master storyteller, who came up with a useful concept you’ll often hear in creative writing classes. And in kind of goes like this:
"If in the first act you have hung a pistol on the wall,
then in the following one it should be fired.
Otherwise don't put it there"
Wikipedia
In other words, everything found in your story better have a function.
For aspiring authors, Chekhov words come as a warning of putting too many unnecessary details into their stories. A gun in a scene means power; it's an object full of meaning and has great potential for plot-twists and conflict, if used correctly. It's not something you would mention and then not use it. If you find yourself giving one extra attention, then you better add significance to it later. Every detail must have a purpose.
Of course, Chekhov wasn’t referring to guns only; the concept is far more extensive than that. The gun can be an object, a setting, a circumstance and even a character. However, make sure not everything happening in your story must function as Chekhov's gun. A mention of large trees doesn't have to mean anything other than, well, a mention of large trees.
There is an art on its own of giving dramatic significance to an object so that it doesn't go unnoticed for your readers, but it doesn't tip them off about what's going to happen next.
Chekhov's concept also comes in handy when you are struggling with the sagging-middle syndrome, and you feel stuck. Overcome this by looking back at earlier chapters and checking for unfired guns hanging on the fireplace. In the worst-case scenario, you won't find any, and you can add one to fire later.
A common mistake aspiring authors make is to interpret Chekhov’s advice too literally, believing that absolutely every detail in a story needs to play a significant role somehow.
And that's probably not the idea you'd want, so instead, use this concept to make sure your story is not being drowned with details that seem more important than they actually are.
