the.com/fourier transform

means A mathematical operation that decomposes a signal from the time (or space) domain into the frequencies and amplitudes of the simple waves that combine to make it.

from Named for Joseph Fourier, a French mathematician and physicist who, in the early 1800s while studying how heat flows through solid objects, claimed any periodic function could be built from an infinite sum of sines and cosines. Other mathematicians of his day were skeptical of the leap, but the idea held up and outgrew its heat-equation origins entirely, eventually becoming the backbone of signal processing, audio compression, image analysis, and quantum mechanics.