Answer:
In this scenario, adding salt to water is equivalent to adding solute (salt) to a solvent (water).
Most solvents have a maximum solute that they can incorporate, and this maximum depends on the temperature, as the temperature increases, also does the maximum (this may be because as the temperature increases, also the space between particles) so if the salt is not fully dissolved when the water is cold, as the water heats up more and more salt will be dissolved, and at the moment where water starts boiling, all or most of the salt will be incorporated in the solution