The World of Your Story
The "world" of your story is an expression that screenwriters use. It simply means, as you might imagine, the environment within which your story is taking place.
Sometimes writers, especially in early drafts, focus so much on character, dialogue, structure and plot that they can skimp on the details of the world itself.
Remember, reading is and always will be a form of "armchair travel". When we become immersed in a book, our imaginations roam in the landscape you create.
Some writing styles are very bare and readers must really fill in the details of the world and this is a conscious choice of the writer. Other writers, especially of yesteryear will sometimes provide almost excruciating detail.
Make a conscious choice, and take advantage of one of the real pleasures of reading; immersion in another world. Where it is cold, marshy and foggy, or a harshly lit office, or a witheringly hot and dusty summer. The world is like another character in your story.
Don't skimp on this important detail.