I want to know the answer to the following question:
What is the principle that is vitally important to understanding the behaviour of a quantity closely related to energy?
All the background I'm provided with is that "When an isolated system is given more degrees of freedom (i.e., given new available energy states that are the same as existing states), then total energy spreads over all available degrees equally without distinction between "new" and "old" degrees.". Is that enough to answer the question?