Accretion is the process by which a body aggregates matter from its surroundings due to its strong gravitational potential. It is the most efficient means known till now for liberating energy. It is believed
to power binary systems, active galactic nuclei etc. My discussion therefore centres on the development
of accretion theory and its applications in astronomical objects. During this I will focus mainly on two
important models of accretion which are the corner stones in the development of accretion theory – 1)
Spherical accretion onto a compact object and the 2) Shakura Sunyaev disk model.