In "Young Goodman Brown," what is the point of view, where does it change, and what is the result of the change?

Point of view in "Young Goodman Brown" is not as simple as it might seem. On the surface of things, the story is told using a third person, limited omniscient narrator—that is, the narrator stands outside the story, narrating events more or less objectively, and able to know the thoughts and feelings of one (or maybe two) characters. You can see this technique in use throughout the story. For example,  consider this passage: 

So they parted; and the young man pursued his way until, being about to turn the corner by the meeting-house, he looked back and saw the head of Faith still peeping after him with a melancholy air, in spite of her pink ribbons.

"Poor little Faith!" thought he, for his heart smote him.

Events seem to be related in a straightforward way here; the narrator even knows what Brown thinks and feels about leaving his wife. The word "melancholy" is a little problematic, though—it is not clear who is making this comment—is the narrator making this judgement, or Brown? And of course it is not clear whether Faith really is melancholy, or just that she "seems" so. 

Such distinctions form the basis for much of the irony in the story, since the problem with point of view is the difference between what the narrator knows and what Brown knows. It is not clear that the narrator agrees with what Brown thinks is happening to him. Take, for example, the pink ribbon that comes to Brown in the forest:

There was a scream, drowned immediately in a louder murmur of voices, fading into far-off laughter, as the dark cloud swept away, leaving the clear and silent sky above Goodman Brown. But something fluttered lightly down through the air and caught on the branch of a tree. The young man seized it, and beheld a pink ribbon.

"My Faith is gone!" cried he, after one stupefied moment.

As with the problematic word "melancholy" earlier, here the narrator does not exactly corroborate what Brown thinks has happened: "something" flutters down, according to the narrator; Brown is the one who "beheld a pink ribbon." In this way Hawthorne is able to suggest that there may be a difference between appearance and reality, and that Brown might not be able to tell what it is. At any rate, Brown's certainty about events is not shared by the narrator, or, presumably, the reader. 

See also:

Hostetler, Norman H.. “Narrative Structure and Theme in "Young Goodman Brown"”. The Journal of Narrative Technique 12.3 (1982): 221–228. Web.