It signifies a balance between the reactant and the products in the reaction.
When noticeable change such as temperature, color, pressure, etc does not show any change, is called equilibrium.
When in a reversible reaction forward reaction and backward reaction because almost equal and no observable change is seen, this state is called equilibrium.
Unstable equilibrium:
A state of equilibrium where even a small disturbance could produce large changes.
A body is said to be in unstable equilibrium when the body does not regain its original position when it experiences an external force.
Example of unstable equilibrium:
The movement of the book will disrupt the position of the ice cream cone when it is placed to rest on its apex on a book. This is an illustration of unstable equilibrium.