# Difference Fourier Shift Theorem and Cross Correlation Theorem

can someone explain me the difference between the Fourier Shift Theorem and the Cross Correlation Theorem?

The shift theorem says that a delay in the time domain corresponds to a linear phase term in the frequency domain

source

So in case of image processing I can find out the shift of two images, which are shifted against each other. I only need to calculate the normalized cross power spectrum of this two images and do an invers Fourier Transform to get the peak, which represents the shift of these to images.

The Cross correlation Theorem says

the cross-correlation between two signals is equal to the product of fourier transform of one signal multiplied by complex conjugate of fourier transform of another signal.

source

So what is the difference between these two theorems?

With both I can for example calculate the shift between two images. I can do it, in both ways, with the Phase Correlation (cross-power-spectrum), right?