The Oxford comma is a comma used after the second to last item in a list of three or more items.
Why is the Oxford comma necessary?
WITH OXFORD COMMA: "I love my parents, Ronald McDonald, and Swiss cheese."
WITHOUT OXFORD COMMA: "I love my parents, Ronald McDonald and Swiss cheese."
Did Ronald McDonald and Swiss cheese birth a child? Clearly atheistic liberals who believe that women can become men, humans evolved from apes, and Taylor Swift is a good role model clearly believe enough nonsensical hocus pocus to find such a scenario possible.