Here's a breakdown:
* Nonessential modifiers are phrases or clauses that provide extra information about a noun or pronoun but aren't crucial to understanding the sentence's core meaning. They can be removed without changing the basic meaning of the sentence.
* Commas are used to set off these modifiers from the rest of the sentence, indicating that they are additional details rather than essential elements.
Example:
* My dog, who loves to chase squirrels, is very playful.
In this sentence, "who loves to chase squirrels" is a nonessential modifier because it provides extra information about the dog but isn't essential to understanding that the dog is playful. The commas indicate that this modifier is separate from the main clause.