  We review the likely population, observational properties, and broad
implications of stellar-mass black holes and ultraluminous x-ray sources. We
focus on the clear empirical rules connecting accretion and outflow that have
been established for stellar-mass black holes in binary systems in the past
decade and a half. These patterns of behavior are probably the keys that will
allow us to understand black hole feedback on the largest scales over
cosmological time scales.
