Mirrors are used by the driver to see behind the vehicle without having to move too much. The side view mirrors are often magnified so the driver can see things more clearly. Side mirrors are part of the body of a vehicle and are usually adjustable, sometimes electronically via a dial inside the vehicle.
The side mirrors are often the least aerodynamic part on a modern passenger vehicle. In some vehicles that run quietly at fast public speeds, the main sound heard inside the vehicle is the wind turbulence generated by the mirrors.
While some racing vehicles remove the mirrors entirely, others use small mirrors which are much smaller than the kind found on a passenger car. They are often a little further away from the body, since the air pressure is higher (more dense) close to the body surface.