Grammar girl here, commas are a workhorse punctuation mark.

They're like the people you ride with on the subway every day.

The delivery guy who comes by your office, and the parents of your children's classmates.

You see them so often that you think you know them just from sheer exposure.

Rarely, does a paragraph go by in which you don't encounter a comma.

But like those familiar strangers, commas are complex.

You might get a sense of them from casual observation.

But to truly know them, you have to dig deeper.

Let's get to know the comma a little better.

Sometimes your subway buddy wears a suit with leather oxfords.

And sometimes he wears jeans with comber's high tops.

His different activities call for different styles.

So it is with the comma.

If you're riding a non-fiction book, you need a tight-laced style, the Oxford comma.

It's orderly, it's clear.

Whoever told you the and takes the place of the comma was wrong.

The Oxford comma, the style recommended by the Oxford University Press and the Chicago Manual of Style,

is the last comma in a series, the comma before the final and or.

He wore a suit, comma, a tie, comma, and oxfords.

He felt hot, comma, sweaty, comma, and tired.

If you're riding something lighter, say, a press release or a newspaper article,

you can get away with a more relaxed style.

...