  Accretion onto black holes is one of the most efficient energy source in the
Universe. Black hole accretion powers some of the most luminous objects in the
universe, including quasars, active galactic nuclei, tidal disruption events,
gamma-ray bursts, and black hole X-ray transients. In the present review, we
give an astrophysical overview of black hole accretion processes, with a
particular focus on black hole X-ray binary systems. In Section 1, we briefly
introduce the basic paradigms of black hole accretion. Physics related to
accretion onto black holes are introduced in Section 2. Models proposed for
black hole accretion are discussed in this section, from the Shakura-Sunyaev
thin disk accretion to the advective-dominated accretion flow. Observational
signatures that make contact to stellar-mass black hole accretion are
introduced in Section 3, including the spectral and fast variability
properties. A short conclusion is given in Section 4.
