Oxford or Serial Comma Use in Lists
An Oxford or
serial comma is a stylistic choice that emphasizes the last item in a
list as being separate from the one immediately before it by separating
the "and [last item]" from its predecessor.
A list in which an Oxford comma would be necessary would look like this:
I love to eat ice cream, and my
grandmother. (a broadly affectionate declaration, vs. the
cannibalistic "I love to eat ice cream and my grandmother.")