to her as the embodiment of pure innocence. He believes in Faith's goodness. When he leaves his home to go to the woods, he leaves his Faith behind, temporarily. He joins the devil in the woods and goes to witness the satanic ritual. However, ironically, he sees Faith there, being initiated. Her pink ribbon represents the mix of sin and goodness that all people have inside of them (red for sin and white for innocence).

The forest represents the dark side of human nature. The sins and failures of the townspeople are exposed in the forest. The devil seems very comfortable in the forest, as do some of the townsfolk they pass along the way. The devil reveals to Brown the secrets of the people's histories and the wrongs they've committed while they walk together in the woods. The ceremony takes place in the forest at night: both the time and the place of this instance are appropriate symbols for the darkness within human nature.

The journey itself represents the process a person takes from innocence to knowledge. Goodman Brown learns about the sins of his community, even though some of them seem on the surface to be good and pure (clergy, for instance). After the journey, Brown is destroyed by what he has learned: he can never live his life peacefully again. However, the other townspeople seem to go on with their lives, able to reconcile their dark sides with the version of themselves they show to others in polite society. 

Archetypes are instinctual and universal reactions to stimuli that is the same across culture and across time.  Carl Jung explains that archetypes are a part of the collective subconscious of man.  In expanding on the first answer, i will address each of your individual items:

Goodman Brown:  The name suggests that Young Goodman Brown could represent any person entering adulthood who attempts to live his life according to the prevailing moral beliefs and codes.  The surname is a common one, implying this universality.  However, the first name, Goodman, also implies a type of naivete on his part.  As he learns, he is not the first member of his family to enter the forest. 

Faith:  Faith as a person does represent faith as a concept.  Beyond that, faith is everyman's "solid rock" so to speak, something to believe in and someone who will always belief in him.  

The Forest:  Archetypally, the forest is a place filled with darkness, chaos, sin, and evil.   Its darkness provides a cover for evildoers, and it houses wild and untamed creatures.  Ironically, Goodman enters this evil to prove that he can overcome it. The reader comes to see that he cannot overcome sin and the devil on his own, particularly if his ancestors and town clergy have been unable to do so.  

Night:  Much like the forest, night is also dark, implying that people can hide their sins under this "cloak of darkness"  and participate in activities they would never dream of doing in the open light of day. It is the time of the devil and goblins.

The Journey:  Everybody is tested.  Everybody wonders if he or she can stand up to the test, particularly the test of good versus evil.  People succeed in proceeding down this path to varying degrees.  Very few, if anyone, succeeds without harm.  As we see, the price of Goodman's journey was his loss of Faith, both literally and figuratively.

The people, objects, and events in this story are, indeed, invested with enough symbolism to justify calling the text an allegory. Salem is a place of apparent order, where all seem to follow the rules and abide by the dictates that keep society from turning into chaos—symbolic of any and every community with its own specific set of rules. The forest is a place outside these rules, a place of lawlessness and, hence, temptation. It symbolizes any temptation that might compel a person to behave in a manner which is out of sync with the rules they desire or purport to follow.

Brown, an everyman character as indicated by his common name, thinks of himself as a "good man" even though he is quite willing to meet and walk with the devil in the forest. Many Puritans did, which, Hawthorne points out, makes it ironic that "Goodman" and "Goodwife" were common titles. His "Faith"—a symbol of his Christian faith—"kept [him] back awhile"—almost preventing him from going into the woods (i.e. from succumbing to temptation). His wife begs him not to go, just as his Christian faith ought to have prevented him, but he ignores both for tonight, intending to "cling to her skirts" from now on and get to heaven that way.

But this is not how faith works—one cannot simply put it down when it becomes inconvenient—and this is not how marriage works either. Thus, we see a failure of Brown's Christian faith on the morning after the witches' sabbath, and we see a failure of his marriage as well, which never recovers.

One of the lingering questions of the story is whether Brown dreams or lives the adventure in the forest. However, in the context of the themes of guilt and sin (and what it means to Brown himself), the dream is as significant as a real experience. And in the context of defining the story elements as an allegory, the symbolism stands whether as part of a dream or reality. In fact, the symbolism can be quite blunt. Brown's wife "Faith" is a good example. 

Faith is his wife's name but also represents his faith in God and his faith in goodness in human (including his own) nature. When he claims he will cling to her and follow her to Heaven, he means this quite literally and metaphorically (allegorically). He is about to leave for the forest and wants to reiterate his loyalty to Faith and his loyalty to faith in God and good human nature. Again, "Faith kept me back a while" is meant literally and figuratively. He uses his faith in order to resist the temptation to face and perhaps be fundamentally affected by the evil and darkness that he might find in the woods. 

The staff resembles a snake and this is clearly a symbolic reference to the Devil, portrayed by a serpent in the Garden of Eden. In this Biblical story, Adam and Eve are tempted to disobey God, just as the devilish man in the forest symbolizes the devil and Brown's own fallibility (note that the narrator says Brown and the old man could be father and son). Like Adam and Eve, Brown is continually tempted to go deeper into the darkness, away from his "faith." 

Brown the "good man" is tempted by evil to stray from his "faith" in goodness and God. This is the extended metaphor or allegory. Portraying other characters as witches or those who worship the devil is also part of the overall allegory that symbolizes the sin and guilt hidden in these seemingly ethical, Christian people. Brown considers himself a "good man" but then discovers his own weakness in straying from God. He comes to see the evil in himself and others. He is so affected (and too unforgiving) that he has lost his faith.