It is true that "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". For example: I went to a party last night. The party was boring, but I enjoyed the fireworks.
In this case the definite article in the second sentence is being used to refer back to the party introduced in the first sentence. This type of reference is called anaphoric.
But the definite article can also be used as a forward-looking (or cataphoric) reference. And this is how it is being used in the Harry Potter text.
This passage from Discourse Analysis For Language Teachers (p42) has the following explanation:
Forward-looking or cataphoric reference often involves pronouns but it
can involve other reference items too, such as the definite article.
The author cites two examples from Newsweek:
... which underline the most characteristic function of cataphoric
reference: to engage and hold the reader's attention with a 'read on
and find out' message. In news stories and literature, examples of
cataphoric reference are often found in the opening sentences of the
text.
The definite article in "the narrow, moonlit lane" has a similar function, namely to entice us to read on and discover the exact setting of this particular lane. Contrast Rowling's sentence with one using articles according to the 'rules' of the web site you refer to:
Two men appeared out of nowhere, a few yards apart in a narrow,
moonlit lane.
It is clear how very much better Rowling's version is.
Universals are always definite (because they are unique), so we don't need 'the'. 'All the' actually means 'all of the', where the set is not universal, but merely the totality of a mentioned subset. All cats are mammals. All [of] the cats at my house are hungry. 'All' is a logical quantifier, which is an inexact (non-cardinal) determiner.
Best Answer
The article "the" indicates that you are referring to a specific instance. So you say, "What is the time?" if you are asking for a specific time. Usually that would mean the time right now, though in context it could mean the time of some event under discussion. (Like, "We're planning a meeting to discuss this. The date of the meeting will be August 12." "Okay. And what is the time?")
Without an article, you would be referring to time in general. If you asked, "What is time?", you would be likely get a philosophical discussion on the nature of time. (Like, "What is time?" "Time is what keeps everything from happenning all at once.")