Why do computers use binary?

1. Three things that I learned is that in order for sound to project form our headphones, a code is sent through our headphones from the jack, computers were originally made to compute and the sound waves go up and down the higher we put our music.
2. I didn't understand the process in which he took 8,324 and tried to show it on a scale and how the sound waves expanded and contracted.
3. One thing i would want to learn more about is how the binary code got started.