The devil has been around in life and literature for a long time. Sometimes his appearance is frightening ("The Divine Comedy" or "Paradise Lost") and sometimes his appearance is much more suave and subtle, perhaps representing the multiple ways that we are confronted with temptation in life. The devil in "Young Goodman Brown" tends to fall into the more casual characterization. He is not presented as a frightening threat, but more as the casual friend of many of the town's leading citizens, including members of Brown's own family. Even at the key moment in the story, the "Black Mass" in the forest, he does not present anything that is particuarly frightening. This is in keeping with the theme that the town's citizens, while appearing just and upright, are secret "friends" of the tempter. On the more subtle side, we should think of this casual acquaintance with the present town members as an indication that their failings may be more "casual" than serious (although he does describe some major sins in his horation in the forest). We never know whether the forest scene acutally happened; we do know that it destoys Brown's life because he can no longer accept even the most "casual" meeting with the devil. If he had been able to accept this as a part of being human, he might have had a good and useful life ... sadly, he could not.
The devil is a universal symbol for evil. Going back to the story of the Garden of Eden, the devil is always presented as a adversary of man and an obstacle to good. Hawthorne came from background that included many Puritans. In fact, one of his relatives was a judge at the Salem witchcraft trials. However, his presentation of the devil is very familiar and similar to other depictions of both his time and earlier literary periods. In "Young Goodman Brown" the devil is very similar to the serpent in the Garden of Eden. He is friendly, cunning and seems rather harmless until the end. This is a pattern that many authors have repeated throughout history.