An archetype is any element of a story (be it a character, relationship, action, or setting) that represents a universal pattern of human behavior. The psychologist Carl Jung saw archetypes as evidence for the “collective unconscious” of humanity; he thought that archetypes showed the shared experiences of the world. As readers, we may enjoy archetypical plot elements because they are easily relatable and familiar. In literature, common archetypes for characters include the hero, the mentor, and the villain.
In the Harry Potter series, Harry is the hero, as he fights evil forces and is predominantly good. Dumbledore is a mentor figure, helping Harry succeed in his quest against the villain, Voldemort. Though archetypes can, like Harry and Dumbledore, be developed, dynamic characters, the role they fill in the story is universal and easily understood.
It would be incorrect to say that Harry is an archetype of a dark-haired wizard with an owl named Hedwig. This is too specific to Harry to be an example of an archetype.
In addition to archetypical characters, there are archetypical situations for a story’s plot to be built around.
The Harry Potter series is broadly about the archetypical theme of good versus evil. Since the series follows Harry through his adolescence, it can also be seen as an archetypical coming-of-age story.