Where is your story set? Mid-town Manhattan? Coastal Maine? Outer space? Whether it's in a house much like you live in or on a planet far, far away setting informs your story.
Good writing uses setting to good effect. Imagine To Kill a Mockingbird without the Jim Crow South or The Good Earth without China and you can see how important setting is to a story. Some writers use setting to enhance story. In 3:10 to Yuma, Leonard Elmore uses the dry landscape of the desert Southwest to illustrate the desperateness of his Characters. In To Build a Fire Jack London uses the Yukon as an antagonist, the thing his character has to overcome to survive.
Think about the book or story you're writing. Are you using setting to an advantage? What about the world you create can you use to improve your story?