The Oxford (or serial) comma is the final comma in a list of things. For example:
The Oxford comma comes right after eraser.
Use of the Oxford comma is stylistic, meaning that some style guides demand its use while others don’t. AP Style—the style guide that newspaper reporters adhere to—does not require the use of the Oxford comma. The sentence above written in AP style would look like this:
Unless you’re writing for a particular publication or drafting an essay for school, whether or not you use the Oxford comma is generally up to you. However, omitting it can sometimes cause some strange misunderstandings.
Without the Oxford comma, the sentence above could be interpreted as stating that you love your parents, and your parents are Lady Gaga and Humpty Dumpty. Here’s the same sentence with the Oxford comma:
Those who oppose the Oxford comma argue that rephrasing an already unclear sentence can solve the same problems that using the Oxford comma does. For example: