Not sure what I'm talking about? Well, here's a definition from Wikipedia:
The serial comma or series comma (also known as the Oxford comma or Harvard comma) is the comma used immediately before a grammatical conjunction (usually and or or, sometimes nor) preceding the final item in a list of three or more items. For example, a list of three countries can be punctuated as either “Portugal, Spain, and France” (with the serial comma) or as “Portugal, Spain and France” (without the serial comma).As for why we still need it, consider this little gem, from a review in The Times of a documentary by Peter Ustinov:
Opinions vary among writers and editors on the usage or avoidance of the serial comma. In American English the serial comma is standard in most non-journalistic writing, which typically follows the Chicago Manual of Style. Journalists, however, usually follow the Associated Press Style Guide, which advises against it. It is less often used in British English. In many languages (e.g. French, German, Italian, Polish, Spanish) the serial comma is not the norm – it may even go against punctuation rules – but it may be recommended in some cases to avoid ambiguity or to aid prosody.
“Highlights of his global tour include encounters with Nelson Mandela, an 800-year-old demigod and a dildo collector."If you like this sort of thing, you really should read the whole Wikipedia article.