  We present the theory of dielectric spectra allowing for homogeneous and
inhomogeneous broadening mechanisms contributions. The dielectric absorption
line shape for oscillators with memory and Debye type relaxors with
distribution of, respectively, resonant frequencies and relaxation times (due
to random electric fields distribution) has been calculated. The conditions of
hole burning observation are discussed. It is shown that the investigations of
the inhomogeneously broadened line shape and width as well as hole burning can
give valuable information about the distribution of random fields and
relaxation times. The latter seems to be extremely important for the disordered
systems like supercooled liquids and relaxor ferroelectrics.
