The sound wave created by a guitar is complex, and it contains a combination of different frequencies. The fundamental frequency of a guitar string is the lowest frequency that the string vibrates at, and it is determined by the length and tension of the string. The other frequencies present in the sound wave are called overtones, and they are related to the fundamental frequency.
The shape of the guitar body, as well as the materials used to construct the guitar, also affect the sound of the guitar. The body of the guitar acts as a resonator, which means that it amplifies the vibrations of the soundboard and makes them louder. The materials used to construct the guitar also affect the sound, as different materials have different acoustic properties.
The combination of all these factors creates the unique sound of a guitar.