The sclera is the correct term for the white part of the eye. Many people get the white part confused as the cornea. This layer is made of tough fibers, protecting the eye from penetration of sharp objects. Using steroids and other drugs may cause this layer to turn bluish in color.
This is the dark unreflective layer, between the sclera and retina, so light doesn't light up the inside and reflect all around inside the eye, contains a rich supply of blood. Imagine a somewhat transparent ball. What would happen if you shine a light through it? It bounces all inside the ball too. For the eye, it would not be too beneficial for the eye to bounce light all around inside, making us see more light than necessary.
This layer is the light and color receptor. It collects light data and sends it to the brain via optic cord. Click here to read a detailed description of the retina.