Describe and define the concept "balance of power" in 1814-1815

The concept of "balance of power" in 1814/1815 is referring to the idea behind the decisions made by the Congress of Vienna.

The Congress of Vienna opened in September of 1814, after the French Revolution and the Napoleonic Wars. All the major nations in Europe were participants, and the purpose of the Congress was to delineate Europe's political map, in a way that could guarantee balance and, at the same time, could restore the "Ancient Régime" (the old monarchies).

The Congress' decisions followed two principles, balance of power and legitimation: the balance of power referred to the principle that stability and security could be achieved only if all the nations have the same power; in this context, power is about territorial supremacy, so new states were made and the borders were adjusted in order to maintain the balance of power. 
The principle of legitimation referred to the decision of restore on the throne the legitimate descendants of the kings deposed during Napoleon's wars.

The Congress closed in June of 1815 and started the "Restoration Epoch" that continued for some years before the new ideas of revolution and democracy would prevail again in Europe.