Which one is correct? A comma can be used to:

separate items in a series

separate an independent clause from a dependent clause

separate two dependent clauses

separate two nouns

Use commas to separate words and word groups in a simple series of three or more items

Use commas to separate words and word groups in a simple series of three or more items. Example: My estate goes to my husband, son, daughter-in-law, and nephew. Note: When the last comma in a series comes before and or or (after daughter-in-law in the above example), it is known as the Oxford comma.