The way we see things depends on the light that your eyes reflect from objects. The eyes focus the light and turn it into tiny electrical impulses that are sent along the optic nerve to the brainand it is in the brain that we actually see things.
1 Additional Answer
Light travels in a straight line. We see things by the help of light reflection on an object. The eye gathers light by using the retina to produce an image and transforms it into a picture that we can interpret. Smooth, shiny surfaces reflect light well while dull and dark surfaces do not reflect light well.