Apposition
From TEFL World Wiki
An apposition is a word or phrase which follows a noun to rename it or describe it in another way. Appositions are usually offset with commas, brackets or dashes.
Her best dish ever, Farfalle a la Trapanese, is a pasta dish.
Angie, the founder of our local network, is only 18.
Don't leave your socks around, or our puppy, Luca, will eat them.
We have an apposition when we use two noun phrases together.
{noun phrase} + {noun phrase}
Diane, doyen of the peripatetic world, got on her bike.
Ace reporter Clark Kent leapt into a phone booth.
In the first example, we do not need doyen of the peripatetic world to understand Diane, so we use commas to separate the two phrases. The sentence would still be acceptable without the second phrase:
Diane got on her bike.
In the second example, ace reporter needs Clark Kent to make the sentence understood so no commas are used. The sentence would not make sense without the second phrase:
* Ace reporter leapt into a phone booth.
