  The properties of the absorption in type 2, narrow line AGNs are reviewed by
focusing on the X-ray indicators. I discuss the properties of the cold
absorbing medium (the putative torus) and of the reprocessed components, as
well as their implications for the unified model. The relation between optical
classification and X-ray absorption is examined. The case of "fossil" AGNs,
whose type 2 classification is not due to absorption effects, is also
discussed. Although this review is mainly focused on nearby Seyfert 2 galaxies,
I also shortly discuss the effects of absorption at higher luminosities and
higher redshift and the implications for the X-ray background.
