  Active Galactic Nuclei (AGN) represent the growth phases of the supermassive
black holes in the center of almost every galaxy. Powerful, highly ionized
winds, with velocities $\sim 0.1- 0.2c$ are a common feature in X--ray spectra
of luminous AGN, offering a plausible physical origin for the well known
connections between the hole and properties of its host. Observability
constraints suggest that the winds must be episodic, and detectable only for a
few percent of their lifetimes. The most powerful wind feedback, establishing
the $M -\sigma$ relation, is probably not directly observable at all. The $M -
\sigma$ relation signals a global change in the nature of AGN feedback. At
black hole masses below $M-\sigma$ feedback is confined to the immediate
vicinity of the hole. At the $M-\sigma$ mass it becomes much more energetic and
widespread, and can drive away much of the bulge gas as a fast molecular
outflow.
