While reading several texts and research articles, I got to know is that the power spectrum shows the power distribution of the signal at different periodicity. However, this concept is very much intuitive when we talk about the signal in time series but I found it a bit difficult to understand the power spectrum of matter distribution in the 3-dimensional space. The texts I have learned so far, just define the power spectrum to be the Fourier transform of correlation function without much interpretation.
What I request to recommend are comprehensive resources that deals with the interpretation of power spectrum in cosmology. It will be much appreciable if the resource explains the power spectral density as well as understanding the statistical features of particle distribution from the $P(k)$ vs. $k$ plot.