What are the parts and functions of a computer keyboard?

A keyboard is comprised of the casing, a circuit board, a membrane, the keys and any other function buttons. The membrane sits between the circuit board and the keys and has a bubble or dome that corresponds with each key and button. When a key is pressed, a contact on the bottom of the membrane makes contact with a pair of contacts on the circuit board, completing the circuit for that key or button. A cable runs from the circuit board, through the casing and to the computer itself, carrying the messages to the computer.