When voltages are applied to materials & circuits, those voltages can change their physical properties, such as closing a circuit which supplies current to a light bulb (causing it to illuminate) or supplying current to a dc-motor which might open up a CD/DVD/Bluray/(?) Drive.
While the answer is fairly complex, and requires understanding the basics of electrical systems & circuits (KVL, KCL), binary numbers, and boolean logic, we can describe the process at a high level: code (represented by plain text words) is compiled, assembled and ultimately translated into a combination of Zeroes and Ones, which represent low and high voltages respectively.
