Dear student,
An equilibrium can either be a dynamic equilibrium, where the reaction is still going on-but this might not be measureable because eventually the rate of the forward reaction will equal the rate of the backward reaction, or a static equilibrium where the reaction has completely stopped.
If a reaction reaches equilibrium the concentrations of products and concentrations of reactants remain constant.
If a reaction reaches dynamic equilibrium the concentrations of products and concentrations of reactants remain constant but both reactions are still going on, just at the same rate.
If a reaction reaches static equilibrium the concentrations of products and concentrations of reactants remain constant because the reaction has stopped.
Regards
Sumit