Cars use a convex mirror or the right side. It bends outward like the a dome. The image will always be right side up and smaller than the actual object but it allows you to see a wider area than a flat mirror.
On the other end are concave mirrors. This is the mirror used at a carnival. The image can be right side up or upside down; larger or smaller than the actual object depending how far you are standing from the mirror.
Eye glasses work on the same principal.
Nearsighted people use concave lenses (thicker at the edges than in the middle)
Farsighted people use convex lenses (thinner at the edges than in the middle)