To use a comma or not to use one, that is the question. Hopefully, you will find this blog helpful in guiding you!
Oxford commas are used to connect the second-to-the-last item in a list of things with the other items in that list. It prevents confusion, such as in the following sentence:
I love my parents, Donald Duck and Daisy Duck. Your parents are ducks???
I love my parents, Donald Duck, and Daisy Duck. I see; this is very clear! You love three different folks. I understand that you are human and your other loves are ducks. (I’m not going there….you must just be a Disney fan.)
Parenthetic expression commas are used in mid-sentence. You have added in an additional thought for clarity in the middle of the sentence, such as the following:
My brother John, who is a good man, helped me move.
Commas are also helpful when you write introductory phrases. For example, I just used an introductory phrase in this sentence. Sometimes folks, especially undergraduates, use too many introductory words or phrases. That can be tedious, so you can flip the sentence around to get rid of the introductory phrase, such as:
I just used an introductory phrase in the sentence above, for example.
I have additional information on commas in this blog, so feel free to read through those blogs and ask questions, if you like.