An Oxford, or serial, comma helps to clarify lists of things. Whether or not you use the Oxford comma is generally up to you. However, omitting it can sometimes cause some strange misunderstandings.
Example: I love my parents, Lady Gaga and Humpty Dumpty.
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:
I love my parents, Lady Gaga, and Humpty Dumpty.
The use of the Oxford comma makes it clear that you love your parents. And you love Lady Gaga. And you love Humpty Dumpty.