  The laws of mechanics of stationary black holes bear a close resemblance with
the laws of thermodynamics. This is not only a mathematical analogy but also a
physical one that helps us answer deep questions related to the thermodynamic
properties of the black holes. It turns out that we can define an entropy which
is purely geometrical for black holes. In this thesis we explain Wald's
formulation which identifies black hole entropy for an arbitrary covariant
theory of gravity. We would like to know precisely what inputs go into arriving
at Wald's formalism. This expression for the entropy clearly depends on the
precise form of the action. The secondary theme of this thesis is to
distinguish thermodynamic laws which are kinematic from those which are
dynamical. We would like to see explicitly in the derivation of these laws,
where exactly the form of action plays a role. In the beginning we motivate the
definition of entropy using the Einstein-Hilbert Lagrangian. We encounter the
Zeroth law, the Hawking radiation, the second law, and then Wald's formulation.
