Definition of Entropy
Entropy is the measure of the thermal energy of a system per unit temperature. This is such a type of energy that cannot be utilized to do some useful work. Work is done only when there is a regular and ordered motion of molecules. Hence, entropy also determines the disorder and randomness of molecules that are present in the system.
Entropy gives us information about those spontaneous phenomena which are occurring around us normally. For reversible processes (they produce maximum work and follow thermodynamic equilibrium), the entropy remains conserved whereas irreversible processes lead to increased entropy.