It’s defined as moles of solute per kilogram of solvent which helps determine how much lower will be new freezing or higher boiling points compared with those pure substances.
Phase Transition: A change from one state (solid, liquid, gas) to another without changing chemical composition.
Supersaturation: A state of a solution that contains more of the dissolved material than could be dissolved by the solvent under normal circumstances. It can also refer to a vapor of a compound that has its (higher) boiling point lowered so it'll condense into solid.