Articles in this area is made up of indefinite and definite.

“a” and “an” are indefinite articles, e.g. a book; an umbrella.

The above 2 phrases means any book and any umbrella; but they are names to some particular objects known as nouns.

Whereas “the” usage comes in 2 forms, basically.

1. When there is ONLY one, i.e. the sun, the boy in the green suit.

2. “The” is also used when the object has already been named and the sentence following it will have to use “the”. E.G. The boy in the green suit is from China.

Same grammarians have indicated “a”, “an”, “the”, can be used as adjectives. This can be explained later.

Your question above the former is making a factual statement using an analogy and the latter is a general statement , which can be proven otherwise.

“The”, as an article, has nothing to do with numbers, like those who say “the” means there is only one of something. If that were the case, none of these sentences would make sense: “The dogs chase the cats.” “The” can be used with either singular or plural nouns – it has nothing to do with numbers. “A” and “an” denote singular adjectives exclusively.

To sum it up, “a” and “an” are general articles used to describe singular subjects and objects (“I am a man in her life” or “they are a new band to see”) while “the” is a more specific article that describes either singular or plural subjects and objects (“I am THE man in her life” or “they are THE new band to see”).

But I think its technically correct either way, sometimes one just sounds better.