The Oxford (or serial) comma is a comma placed between the last two items in a series of three or more. For instance, “I like cake, pizza, and ice cream.” Proponents of the Oxford comma argue it’s necessary to avoid potential ambiguity. It is also placed before the conjunction “and ” or “or”. There is a hot debate around its use because this is technically an optional punctuation mark, and in some sentences it clearly helps understanding and removes ambiguity while in others it can be reduntant.