Initially when we dissolve a solute , rate of dissolution is far exceeding the rate of deposition. But as the concentration of solution increases , the rate of deposition also increases and a situation comes when rate of dissolution becomes equal to rate of deposition that situation is called dynamic equilibrium.
Saturated solution:
It is the solution in which dissolved solute is in dynamic equilibrium with undissolved solute, if we dissolve more solute into it it will not dissolve.
Unsaturated solution:
This solution contains less amount of solute than the equilibrium amount of it. If we dissolve more solute into it , it will dissolve.
Supersaturated solution:
This solution contains more amount of solute than its equilibrium concentration. These solution are unstable.