Commas are vital to writing clarity. There are several uses for commas, including separating distinct parts of a sentence and distinguishing between items in a list. The above-referenced Oxford or serial comma is used for this latter purpose. For example, you might list things you love, including your parents, J. R. R. Tolkein, and Abigail Adams. With the Oxford comma, it is clear that this list includes three separate entries. Without it, the sentence indicates that your father wrote The Hobbit and your mother was the Second First Lady of the United States. The comma thus is a handy little piece of punctuation.