A theoretical approach providing the shape of the spectrum of dipolar fluctuations (Fourier transform of the longitudinal component of magnetization) and shape of the wings of NMR absorption in condensed matter has been elaborated. It is shown that the spectral contours are exponentials with the same decay constant. The results obtained explain for the first time the known experimental data and establish a connection between two groups of different experiments. The theoretical prediction is in good agreement with experimental results.