When light bends as it passes through transparent substances it is called refraction. Another way that light bends is by reflection.
You can see some objects because they give off their own light e.g. lamps, fires, and the sun. They send light directly to your eyes. But, most objects do not give off their own light. You see these objects because light (from a light source) bounces off them before it enters your eyes. This is called reflection, and it works similar to a ball bouncing off a wall.
Although light bounces back from every object it hits, some items reflect so much light, (and absorb very little) that we can see an image on them. Reflected light is also what makes things sparkle and shine. Mirrors produce the best reflections, because they are smooth and flat. Generally smooth surfaces are better materials for reflection than surfaces that are uneven. Outward curved (convex) mirrors can change the size of images, and concave mirrors (curved inward) can flip images upside down.
Thanks to Light Optics/actrefle at Tripod for its pictures and diagrams.