Often we’re taught to use commas is we pause when speaking. While that can be helpful, generally commas aren’t about showing how a person should say a line of text. Instead, authors use commas to subtly signal a variety of information to readers, and how we convey that when speaking may not correlate at all to what is done when writing.
One bit of information commas signal to readers is that we’ve included additional details that do not affect the meaning or understanding of the sentence. In short, these details could be deleted from your sentence (and if you’re trying to make a word count and need to cut, such details are perfect for that). Usually such information appears in the middle of a sentence. These details are known in grammar parlance as nonessential clauses.
An example would be who is in my class in the sentence Jane Johnson, who is in my class, scored the most points in last night’s game. That Jane is in the writer’s class is unnecessary for understanding the point of the sentence, which is that she was the highest score in last night’s game. Because of this, who is in my class must be set off with commas.
My name is Rob Bignell. I’m an affordable, professional editor who runs Inventing Reality Editing Service, which meets the manuscript needs of writers both new and published. I also offer a variety of self-publishing services. During the past decade, I’ve helped more than 300 novelists and nonfiction authors obtain their publishing dreams at reasonable prices. I’m also the author of the 7 Minutes a Day… writing guidebooks, four nonfiction hiking guidebook series, and the literary novel Windmill. Several of my short stories in the literary and science fiction genres also have been published.