Lets start with Fourier Transform as a tool that breaks a wave into a different form. Some say “everything in the world can be described via a waveform” e.g. TV signal, cell phone signal, music and every waveform can broken down into a sum of sinus functions of different frequencies (bands).
- Time domain = amplitude vs. time
- Frequence domain = amplitude vs. frequence
A simple form of considering the sinus function is unit circle. The unit circle has the circle distance of “1” (or the respective part of e.g. 1/ 2). The sin(α) is just the amplitude hight in the frequence domain. Different frequences are just circle with different distances (distances <= 1). Also called different frequence bands.
The respective time domain value is the addition/ sum of both sinus values.
The other way around it is about wrapping it up on a circle with a specific speed. The speed is measured by unit circle/ second. If e.g. a wave is constructed by a 3 Hz and a 2 Hz wave the value of the e.g. x coordinate center-of-mass has a maximum (positiv) peek at 3 and 2 cycle/ second.