How do door locking mechanisms work?

The most commonly used locking mechanism consists of pins, tumblers, and a rotating cylinder. There is an upper and lower row of varying length pins that make contact with each other when the key is not in the lock. The upper pins are spring-loaded. The notches in a key vary in length to correspond to a specific pin. Inserting the correct key into the lock and turning rotates the cylinder breaking the contact between the pins to unlock the door.