Explain third law of thermodynamics.

Hint:Third law thermodynamics is regarding minimum values of entropy of a system. It says that there will be some residual entropy even when system approaches near$0$K

Complete step by step answer:
Third law of Thermodynamics states that:
The entropy of a system approaches a constant value as its temperature approaches absolute zero.
This law is regarding properties of closed systems in thermodynamic equilibrium.
One more statement of third law of thermodynamic is given by Nernst-Simon:
The entropy change associated with any condensed system undergoing a reversible isothermal process approaches zero as the temperature at which it is performed approaches $0$K.
Additional Information:
-The zeroth law of thermodynamics states that if two thermodynamics system $A$and $B$are each in thermal equilibrium with a third system\[C\], then\[A{\text{ }}and{\text{ }}B\]are in thermal equilibrium with each other.
-Isothermal process takes place at constant temperature, Isobaric process takes place at constant pressure and Isochoric process takes place at constant volume.
-The first law of thermodynamics also called the law of conservation of energy states that the energy can be transformed from one form to another, but can be neither created nor destroyed.
-Second law of thermodynamics states that it is impossible to derive a continuous supply of work by cooling a body to a temperature lower than that coldest of its surrounding.

Note: Another alternate statement of third law of thermodynamics can be:
It is impossible for any process, no matter how idealized, to reduce the entropy of a system to its absolute-zero value in a finite number of operations.