Cornea
The cornea which acts like a camera's aperture & referred to as the ‘front window of the eye. It provides most of the focusing power when light enters your eye. The cornea is transparent structure which is composed of 5 layers of tissue. The outer layer (the epithelium) is the eye's protective layer. This layer is made up of highly regenerative cells that have the ability to grow back within 3 days, and therefore, allow for fast healing of superficial injuries. Most of the inner layers provide strength to the eye. The laser vision or R.K correction procedure is performed on this part of the eye. (Cornea Infections)
Sclera
This is the 'white part' that we see in people's eyes. The sclera's purpose is to provide structure, strength and protection to the eye.

Iris
The colored part of the eye mostly brown, black & blue. The iris helps in regulating the amount of light that enters the eye with  contraction or expansion of the muscles of the iris.
Pupil
Acts like a shutter of camera, situated in the middle of the iris. The pupil determines how much light is let into the eye. It changes sizes to accommodate for the amount of light that is available. When you are in a bright environment, the pupil becomes smaller to allow less light through. When it is dark, the pupil expands to allow more light to reach the back of the eye.
Lense
The transparent structure located behind the pupil which help in focusing light rays over the retina. As people reach their 60’s or 70’s, the lens sometimes becomes cloudy and hard (cataract formation), preventing light from entering the eye.