Its easy to understand the eye when you compare it to your camera.

The eye is like a camera in which lenses focus the picture on a light sensitive film.

In the human eye the transparent cornea and lens focus images on the retina, a thin light sensitive film which receives light and changes it into electrical signals which are then transmitted to the brain by the optic nerve.

Just in front of lens lies the iris ('colored portion of the eye- to help you understand , Aishwarya Rai  has a slightly green iris !!!) with a central opening - the pupil. This is just like the shutter or diaphragm aperture of the camera and helps regulate the amount of light entering the eye.

The sclera ('white of the eye') is the protective outer coat of the eye. Between the sclera and the retina lies the choroid, which has a chiefly nutritive function. The space between the lens and the retina is filled with a clear jelly called the vitreous body.