  A brief summary of the properties of astrophysical black holes is presented.
Various modes of accretion are distinguished, corresponding to accretion at
rates from well below to well above the Eddington rate. The importance of mass
loss is emphasized when the accreting gas cannot radiate and it is asserted
that a strong wind is likely to be necessary to carry off mass, angular
momentum and energy from the accreting gas. The possible importance of the
black hole spin in the formation of jets and in dictating the relative
importance of non-thermal emission over thermal radiation is discussed.
