Have you ever thought about "comma"? Yes, I mean "Oxford comma."
The "Oxford comma" or a "serial comma" is an optional comma before the word 'and' at the end of a list. The definition comes with a word "optional" which means it's up to you if you want to use it or not. As it was traditionally used by printers, readers, and editors at Oxford University Press, they started calling it the Oxford comma.
Knowing it a bit closer will make you realize the importance of using it. Let's see how the world would be if it doesn't exist.