Saturated Solution - the solute is completely dissolved in the solvent and no more solute can be dissolved.
Unsaturated Solution - its a solution that hasn't reached it's limit and can still dissolve more solute.
Supersaturated Solution is when you put solute in the solvent in excess. When you put the solute in a large amount, it might not dissolve into the solvent. The solvent will not be able to absorb the whole solute, because there is too much.