Here's a breakdown:
* Appositive: A word or phrase that renames or identifies another noun or pronoun.
* Restrictive: Essential to the meaning of the sentence. It limits the noun it modifies. No commas are used.
* Non-restrictive: Provides additional information that is not essential to the sentence's meaning. Commas are used to set it apart.
Examples:
Restrictive (no commas):
* The author Stephen King is famous for his horror novels. (There are many authors named Stephen King, this one is the famous one)
Non-restrictive (commas):
* Stephen King, the author of "It", is famous for his horror novels. (We already know who Stephen King is, the appositive just adds extra information)
Key Point: If you can remove the appositive and the sentence still makes sense, the appositive is non-restrictive and needs commas.