Pasta is Sherry’s favorite food, so she learned to cook.

In the given sentence, favorite food renames the word pasta.

Hence, favorite food is the appositive.

The chief editor, Roy, resigned from his post.

In the given sentence, The chief editor is the noun phrase that renames Roy.

Hence, The chief editor is the appositive.

My younger brother Steve’s office is in New York City.

In the given sentence, My younger brother is a noun phrase that renames Steve.

Hence, My younger brother is the appositive.