Acids are hydrogen (hydronium) ion concentration enhancive chemicals when they are dissolved in water. They are diversed in two groups; organics and inorganics. Organic acids are generally found abundantly in living beings and they are not too hazardous. Inorganic acids, however, are highly irritant and have serious corrosive effects on metals.
All acids perform neutralizing reactions to form salt and water in bases. Their pH value is lower than 7. They are irritant for skin and their taste is sour.
Acids, like alkalies, form the foundation of chemistry and they are used in many reactions, both as raw material and catalyst.