Not all mirrors are flat. The back and front of spoons, for example, behave as curved mirrors.
Curved mirrors show you a view which is very different from real life. A bulging (called convex) mirror makes things smaller. These mirrors are used for security and car wing mirrors, for example.
A dished (or concave) mirror gives a narrow field of view. They are used as vanity mirrors, and you also find them behind every torch bulb.