Here's why:
* Nonessential elements are phrases or clauses that add extra information but are not crucial to the meaning of the sentence. They can be removed without changing the core meaning.
* Commas are used to separate these elements from the rest of the sentence, indicating that they are optional additions.
Example:
* The dog, which was very fluffy, barked at the mailman. ("which was very fluffy" is a nonessential clause, and the sentence still makes sense without it.)
Let me know if you'd like more examples or have any further questions!