An appositive is a noun or pronoun that renames or clarifies another noun or pronoun. It's usually placed right next to the word it's explaining, and often set off by commas.
Here are some examples:
* My dog, a golden retriever named Buddy, loves to play fetch. ("a golden retriever named Buddy" is the appositive that explains "dog")
* The capital of France, Paris, is a beautiful city. ("Paris" is the appositive that explains "The capital of France")
* My favorite author, Stephen King, writes suspenseful novels. ("Stephen King" is the appositive that explains "My favorite author")
Appositives can be useful for adding information, providing emphasis, or making your writing more concise.