As it dissolves a large number of solid, liquid and gaseous substances it's called a universal solvent. It's important for living thing because all of them depend on water to survive. For example, many organisms live in the water and they find some of the nutrients that are necessary for live dissolved in water - gases included.
If a saturated hot solution is allowed to cool, the solute is no longer soluble in the solvent and forms crystals of pure compound. Impurities are excluded from the growing crystals and the pure solid crystals can be separated from the dissolved impurities by filtration.
