Hawthorne's story is a great example of an allegory. In an allegory, most of the items, characters and events carry real significance as well as symbolic significance. Another way to answer the question is to point out the story is written in the period of American Romanticism. This literary movement frequently explored the idea of the power of the human imagination; the inherent goodness of man, the power of nature; the nature of good and evil. The list could go on, but those themes are clearly present in this story. In "Young Goodman Brown" you can see the connection between the two topics above. The good vs. evil is presented though the symbolism of the woods, through Faith's pink ribbon, through the trees on fire at the witch's meeting, and the characters of Goodman Brown, Faith, and the old man (devil). For each theme, there will be symbolic elements that illumate Hawthorne's meaning.
The undeniable reality of the story is that Brown’s journey is a dream, or nightmare. In psychological terms, Brown may be schizophrenic, because his view of others is distorted by his nightmarish convictions. It is probably best, however, to stress that his gloom results from religious fanaticism. This might somewhat difficult to grasp as the story is in an unusual language and that it is cloudy in its comprehension for some of the details are more symbolic than anything else and that its sequence of events can be difficult to follow.