Who is the narrator? How do you think the narrator knows so much about Emily? Why does he/she use "we" instead of "I"?

The narrator of the story is unidentified, but he/she represents the voice of the town. The narrator is so well informed because "they" have been around Emily all their lives..... it's a small town. The narrator uses "we" because as I have already stated..... "we" is the collective voice of the townspeople.