  The differences among apparently diverse classes of AGN are mainly the result
of viewing the central engine at different orientations, because dust, which
absorbs and scatters the light, partially covers the central source, and
because synchrotron emission is highly beamed along the relativistic jet. Also
important are factors independent of orientation: the total power output, the
unknown mover behind the eigenvector 1 relationships, and the radio-loudness.
These other factors may not be independent of the parameters of Unified models,
such as intrinsic jet physics, AGN dust content, and torus thickness. We
outline the basic evidence for orientation Unified Schemes, and briefly discuss
their importance for understanding the mechanisms of the central engine and its
relation to the surrounding host galaxy and beyond.
