Is for see the colors movements and the distance of objects with our eyes.
The first part is called cornea, then it have the pupul that it's protected by the cornea, then the lens focuses the light on to retina, the cornea protect the iris too, the retina is made up of nevous tissue and thin layers of cells, it light asnd colors and finally the optic nerve that transmit infomation from the retina.
Check this video in Spanish about the Sight.