What is an oxford comma?/ Is it necessary to put a comma before the last item in a list?

使用一个逗号前最后一项lis)t is known as the Oxford Comma, sometimes the Serial Comma. It is used before conjunctions in a list like this with three or more items. Its use is purely written style and optional. For example: pen, paper, scissors, and stapler. At some places, using the Oxford Comma is necessary. Look at this sentence: I love my parents, Lady Gaga and Humpty Dumpty. Now here, it seems as if the parents are Lady Gaga and Humpty Dumpty. But if we use the Oxford Comma, the sentence will be: I love my parents, Lady Gaga, and Humpty Dumpty. If the Oxford Comma is not used, the whole meaning of the sentence changes.