Equilibrium refers to a state of stable conditions where factors remain constant with little inherent tendency for change. It can refer to market equilibrium where the amount buyers want to buy matches what sellers want to sell at a given price. There are two types of equilibrium - static equilibrium which is keeping the body upright and stable without movement, and dynamic balance which is keeping the body upright during movement by opposing forces regulated by the central nervous system. Examples include maintaining balance while standing or moving.