If after an author describes a short story's location or setting, he addresses the reader as "you," he is using mode.

the Second-person Narrative

Explanation:

The narrative modes a write may use include:

the First-Person Narrative: this is when the story is narrated using "I." Here, the author assumes the viewpoint of the protagonist, or the main character and uses "I" to reference this person.

the Second-person Narrative: this uses "You" to describe the protagonist. This is not as common as the other forms and is a way to draw in the audience.

the Third-person Narrative: this is a common form of narrative that uses "he", "she", "they" to describe the protagonist(s).