Sound is produced by a wave that is an oscillation of the pressure within solid, liquid or gas.
Humans can detect sound with their eardrum. When a person hears a sound, they detect differences in the pressure of air particles.
As the frequency of a sound wave increases it's pitch increases. The amplitude (y value) determines the intensity of the sound. The greater the amplitude, the more intense the sound.
There is no sound in the vacuum of space because there is no medium that can be oscillated in order to carry a sound wave.