DVDs work like CDs work. A motor spins it and the disc is spun at a speed determined by the DVD you are using. Laser assembly is used to read the data, video and audio. There is a laser beam and a light sensor used to read the reflected light. The tracking mechanism is used to move the laser beam in sync with the DVD so it can track the DVD perfectly. The tracking device is very important as the lasers must track the data or it will not read. Data is in digital form using 1s and 0s formed as bumps and flats. It is aluminum with plastic coating which is used to reflect the data. The laser beam projects onto the DVD and the motor spins to read it.