Here is some link
fast Fourier Transform

If one consider the Price verse time as a wave. After transform it will gave peaks as frequencies, which will give us information about how long will take for each price peaks or bottoms will occur. All kind of filters can be used to filter out noise.
It is hard to plot the gragh on price chart since it has to display on peak verses 1/time graph.
There some other ways to use it. That is reverse transform the frequency peak back after some filters have been added. This will give us smoothed
price peak without delay (hopefully).
FourierTransform has been intensively used in the spectrometers field.