Salts are compounds that contain positively charged ions (cations) and negatively charged ions (anions) held together by electrostatic forces. Examples of salts include sodium chloride (NaCl), potassium nitrate (KNO3), and calcium carbonate (CaCO3).

Acids are substances that, when dissolved in water, release hydrogen ions (H+). Examples of acids include hydrochloric acid (HCl), sulfuric acid (H2SO4), and nitric acid (HNO3).

Bases are substances that, when dissolved in water, release hydroxide ions (OH-). Examples of bases include sodium hydroxide (NaOH), potassium hydroxide (KOH), and calcium hydroxide (Ca(OH)2).

Solutions are homogeneous mixtures of two or more substances. When a salt, acid, or base is dissolved in water, the ions separate and become dispersed throughout the solution.

Ionic liquids are liquids that are composed entirely of ions. They are typically formed by melting a salt or by dissolving a salt in a polar solvent. Ionic liquids have a variety of applications, including as electrolytes in batteries and as solvents in chemical reactions.