Conservation Law refers to principles in physics that state certain quantities remain constant in isolated systems. For example, the Law of Conservation of Energy asserts that energy cannot be created or destroyed, only transformed from one form to another. This means that the total energy in a closed system remains the same over time. Another important aspect is the Law of Conservation of Momentum, which states that the total momentum of a closed system remains unchanged unless acted upon by an external force. These laws are fundamental in understanding how physical systems behave and are essential in fields like mechanics and thermodynamics.