In the field of English, we use the MLA style guide, which employs the Oxford comma (or the serial comma). This is the comma that connects with the conjunction that precedes the final item in a series. Some formats do not use this comma, such as the AP style that newspaper writers use. However, a recent court case has proven that this puny punctuation can be a very big deal. One company will be paying its employees millions of dollars more than they had planned because of a missing comma in its contracts.
Commas help provide clarity, and I believe the MLA style is correct. Here's why: