Animation showing harmonics of a wave. Each harmonic is an integral (whole number) multiple of the 1st harmonic (or fundamental frequency). An oscillator (such as a guitar string) can vibrate at different frequencies. In reality, all of these vibrations would be happening in the same string, but they are separated out for clarity. The lowest frequency (in red at the bottom) is called the fundamental frequency. The still points or nodes (orange balls) occur at points where the troughs and peaks cancel each other out (as a result of interference, which is how standing waves are created).