Acids are the hydrogen containing substances that give H+ ions in water solution, tastes sour, change the color of the indicators (red litmus paper to blue). It reacts with metal like iron, zinc, aluminum to liberate hydrogen, reacts with certain bases to form salts. Hydrochloric, sulfuric, nitric acid is the most common examples of inorganic mineral acid used widely in the laboratory and industry. The modern acid and bases are not only limited to the aqueous solutions (Arrhenius theory), the electronic concept (Bronsted Lowry and Lewis theory) is also used to define all the acids and bases in chemistry or chemical science. In this category, we discuss the definition and properties of acids and bases by different concepts or theories.