Serial comma is a:
…comma used immediately before a conjunction (such as “and” or “or”) in a list of three or more items. The phrase “ham, chips, and eggs” is written with a serial comma, but “ham, chips and eggs” is not.
So what? you say. Well, it’s a big deal for editors and many writers.:
People who know nothing else about punctuation recite this error with conviction, which says something ominous about the state of English language instruction. Why have many English teachers taught this wrong rule? Are they truly unaware that press style is for journalists and that we have a wealth of better authorities for standard American usage?
I use the serial comma. “He ate a sandwich, bag of chips, and a cookie” makes more sense to me than “He ate a sandwich, bag of chips and a cookie”.