  Seyfert galaxies have been shown to exhibit a large variety of features in
their X-ray spectra from which the environment of the central engine can be
deduced. We focus on the two following aspects: the Warm Absorber, mainly
responsible of the soft X-ray properties, and the reprocessing/reflecting
plasma medium at the origin of the iron Kalpha fluorescent line. The physical
parameters and the location of the so-called Warm Absorber (WA), a photoionized
medium along the line of sight to the nuclear region, are more strongly
constrained by optical coronal lines than by the oxygen edges observed in the
soft X-rays and produced by the WA. The photoionization models also predict the
intensities of the X-ray emission lines which are going to be detected with the
new generation of X-ray satellites. An alternative model to the relativistic
accretion disc is proposed to explain the profile of the X-ray iron Kalpha line
observed in the Seyfert 1. This line can be formed in the framework of a
quasi-spherical accretion of optically thick clouds. An optically thick
photoionization code coupled with a Monte-Carlo code has been developed to
compute the entire spectrum from the IR to the hard X-rays for a close geometry
with a large covering factor. The multiple Compton reflections allow to
reproduce the redshifted broad iron line as detected in several Seyfert 1
galaxies and in MCG-6-30-15.
