What is the process when a snake remove it skin?

The common name is shedding, or sloughing. The technical term is ecdysis. Basically, when a snake 'outgrows' its skin, it secretes a fluid (mainly composed of vitamin A) between the current layer, and a new layer of skin underneath. This is what turns the snakes eyes a milky blue-white. After a few days, the snake breaks the skin (usually at the mouth) and crawls out of it - turning the skin inside-out in the process.