An appositive phrase is known to be a group of words that actually comes before or after a noun or pronoun in order to explain, buttress or modify it.
These appositive phrases may be omitted from a sentence. When this omission is carried out, it doesn't affect the noun or pronoun it identifies. We say it nonrestrictive.
From the sentence given, we discover that "The famous guitarist" is the appositive phrase explaining who Nathan Heywood is.
