Most modern mirrors are made of smooth layers of silver or aluminum along with other chemicals and coatings to aid in their construction. While the chemical properties of silver play some role in reflecting light, the fact that these layers are very, very smooth is more important here. If the surface of the silver layer were rough, the light would be reflected in a variety of different angles, which you would see as a distorted image. When the surface is perfectly smooth, the light bounces straight back into your eye and you see an accurate reflection of the object. This is why you can see clear reflections in very still water or a shiny piece of leather—both are smooth surfaces.