Evaporation is another separation technique which separates a liquid from a solid. Evaporation removes the liquid leaving the solid behind. This is useful when you want to separate a soluble (will dissolve) solid from a solvent (liquid). Evaporation could be used if you wanted the salt in your salt water mixture.
Here, you would need to raise the temperature of the mixture to the boiling point of the liquid component. Then, the liquid would evaporate off leaving the solid behind. Heating the liquid increases the kinetic energy of the molecules of the liquid so that the molecules have enough energy to break away and separate, forming a gas.
Some molecules will have enough energy to do this anyway, but it takes time. Heating the substance increases the kinetic energy of the molecules so that more of them break away at the same time reducing the time taken.