"Barn Burning" is told from the point of view of an objective third person, who knows something, but not everything, about the events that transpire and the characters who are involved. But there's a lot more going on in this narrative when it comes to voice and point of view.
William Faulkner is known for his tricky narrative structures. We detect four main layers or streams of narrator point of view in "Barn Burning." Compared to his longer works like As I Lay Dying and The Sound and the Fury this story is a piece of cake. In fact "Barn Burning" is good preparation for tackling those more complicated works.
First, the narrator is concerned primarily with Sarty. Sarty is in every scene and is always the focus of the story. In short, the narrator is seeing everything through Sarty's eyes and even reading Sarty's thoughts.
This brings us to stream two, Sarty's thoughts. Notice that all of Sarty's thoughts are italicized, while words he speaks aloud are not. This lends an added layer of reliability to the story. Knowing what Sarty is actually thinking helps us understand him. Consider this example:
"I could run on and on and never look back, never need to see his face again. Only I can't. I can't […]" (86)
This is an effective way of conveying Sarty's turmoil to the reader and clarifies something in the process. In this moment Sarty has made a choice. He never wants to see his father again. We wonder if he changes his mind when he gets older. What do you think?
The third level tells us things about Sarty's future. Not much, but enough to let us know that Sarty lived to be at least thirty, and that the memory of his past never left him. This perspective of the story important in part because it lets us know that Sarty survives, that he makes some kind of life for himself. This knowledge lends a certain hope to "Barn Burning."
Finally, a fourth narrative stream tells the reader things that Sarty doesn't know, or might know if he was older. This gives us information on Abner (that he was a mercenary; that he hid in the woods for four years) that builds his character. Equally important, this narrative perspective allows the narrator poetic voice or artistic liberty.
The narrative voice can't be contained by the vision of the characters. For example, Sarty will never know that it was midnight when he was sitting on the hill. However, this bit of information gives the story a certain symmetry. Sarty is at a mid-point or turning point in his existence. We could recognize this anyway, but by telling us that it's midnight, the narrator dramatizes the fact.