A salt is a crystalline material consisting of positively charged cations and negatively charged anions, and is electrically neutral as a whole. Table salt or sodium chloride (NaCl) is the best-known example. Salts often have metals such as sodium, potassium and magnesium as cations, and non-metals such as chlorine, acetate (CH₃COO^–) or sulphate (SO₄^2-) as anions. While salts as crystals in the solid state do not conduct electricity, they do so as solutions in water or in the molten state.

Salts have many similarities with ceramics. Both are solid, crystalline materials that often possess ionic bonds (with the covalent silicon carbide as an exception), and with a high melting point. On the other hand, the anions in ceramics are often limited to oxides, nitrides and carbides, and ceramics are usually not water-soluble. In practical terms, you can often say that a salt is stored as a powder or compound in a utensil made of ceramics.

Graduation towers such as the one here in Bad Rothenfelde, Germany, were used around the 18th century to concentrate salt solutions from saltwater springs by allowing them to flow downwards along thorny branches, with sunlight, heat and wind evaporating some of the water. These naturally concentrated salt solutions were further processed in saltworks for salt production in those days.