The narrator of The Scarlet Letter is an omniscient one who examines the characters and tells the story in such a way that the reader knows that he knows more about the characters than they even know about themselves. Although he is omniscient, he is also a subjective narrator, which means that the reader inputs his own opinions of things of things.
Hawthorne's "The Scarlet Letter," is told from the point-of-view of the author. It should be understood that this is the author-as-character, not Hawthorne himself.
The introductory chapter, "The Custom House," tells that the narrator has experienced "an autobiographical impulse" that has "taken possession of me."
One day, in his dreary work, the author makes a perplexing discovery. Among the miscellanea he combs through in the custom house, one article particularly catches his eye. In a confessional tone, he says:
But the object that most drew my attention, in the mysterious package, was a affair of fine red cloth, much worn and faded. There were traces of gold embroidery...It was the capital letter A.
The mysterious item leads the narrator to discover its tragic past and the history of one of literature's most enduring and compelling characters: Hester Prynne.