It is an interactive aspect of your fictional world that saturates the story with mood, meaning, and thematic connotations. Broadly defined, setting is the location of the plot, including the region, geography, climate, neighborhood, buildings, and interiors. Setting, along with pacing, also suggests passage of time. Place is layered into every scene and flashback, built of elements such as weather, lighting, the season, and the hour.
Sorry for the late reply, but it's better late than simply not answered.