Extracting salt and other minerals from water is desalinization. Desalinization is necessary to make ocean water drinkable. If you think there's a chance you'll get marooned on a desert island someday, you might want to read up on it.
Desalinization is the process of removing minerals—and in fact, it often refers to the preparation of soil for planting. If soil is too high in salt, plants won't grow in it. Likewise, water that undergoes desalinization can be used to irrigate food crops. Because of the worldwide shortage of clean water, desalinization is becoming more common; in places where water is too polluted to drink, desalinization and collecting rainwater are the only methods of providing people with safe drinking water.