Question

what is equilibrium?

Answer 1

Equilibrium means when the concentrations of reactants and products are in an unchanging ratio. Another way of saying this is that a system is in equilibrium when the forward and reverse reactions occur at equal rates. 

Answer 2

chemical equilibrium is the state in which both reactants and products are present in concentrations which have no further tendency to change with time. Usually, this state results when the forward reaction proceeds at the same rate as the reverse reaction.