Which mirror helps the driver see behind the car?

Side mirrors show rearward. So it's not OK to choose between rearview and sideview answers.

There's a song, sung by Meatloaf and written by Jim Steinman called "Objects in the Rear View Mirror may Appear Closer than they are" Love that song!

little b, Sorry that doesn't make sense.

Called auto racing’s greatest invention.

I've not been in the rearview mirror