Student or Learner
The two men appeared out of nowhere, a few yards apart in the narrow, moonlit lane.
-Chapter 1 of Harry Potter and the Deathly Hallows: The Dark Lord
According to this web site, English native speakers use the definite article in front of a noun when they believe the hearer/reader knows exactly what they are referring to. But the sentence above is the very first sentence in Harry Potter and the Deathly hallows. We don't know anything about the two men and the narrow, moonlit lane.
I looked up the use of the definite article on books and the Internet. But I couldn't find out why the definite article is used in front of that nouns.
Could you explain why the definite article is used?
Your definition covers only one use. Commonly, the definite article is used before nouns that name a specific thing or things. The two men were specific men (not just any men) and and the lane was a specific lane (not just any lane.
Pope of the Dictionary.com Forum