What is Le Chatelier's Principle?

Le Chatelier's Principle states that if a system at equilibrium is disturbed by a change in temperature, pressure, or concentration of reactants/products, the system will adjust itself in order to counteract the effect of the disturbance and restore a new equilibrium state. In other words, when a system is subjected to a stress, it responds by shifting the equilibrium in a direction that minimizes the effect of that stress.