The boy next door is an archetype of storytelling. He is often invoked in Western contexts to indicate wholesome, unassuming, or "average" masculinity. He is a young man with a sweet, shy demeanor who is just discovering his physical and spiritual strengths. The boy next door maintains his innocent wonder due to his charm, sincerity and preservation of virginity. He is never arrogant and mostly reserved. He is the male counterpart of the "girl next door." An example of each is found in Thornton Wilder's Our Town, in the characters of George Gibbs and Emily Webb.
There is a set of typical relations he may maintain in the story. The boy next door is often, but not always, the protagonist of a story. As such, his innocence, sincerity, and common origin will often be contrasted with the cleverness, hypocrisy, and privilege of the antagonist. The boy next door may have a sidekick, who shows somewhat less promise than the boy next door; this will serve to heighten his appeal by contrast.
A boy next door may serve as a love interest for a female protagonist. In this case, he is most likely someone the protagonist has known for most of her life, but in the past couldn't appreciate because of her age. As a love interest, the boy next door is always physically close, yet at the same time detached from the protagonist. He is the sweet boy the protagonist sees everyday, a really great friend, or the perfect boy to bring home to her parents.