Which best describes dynamic equilibrium

Equilibrium is best describe by a reaction. Equilibrium exists for a reaction when as time goes to infinity there will be no change in the system at that certain conditions. There are two types of equilibrium : dynamic equilibrium and static equilibrium. Static equilibrium happens when all particles are at rest or has no movement. This can also be termed as a steady-state system. On the other hand, dynamic equilibrium happens when the forward reaction rate is equal to the backward reaction rate. In short, dynamic equilibrium is a reversible reaction while static equilibrium is an irreversible reaction. 

Mg is used to measure mass