Organic chemistry means how particular reagents will react. Example if we considering acid it will make a proton donor or an electron acceptor. That is when was an acid is added it would acidify the medium by donating the proton. Similarly base will add hydroxyl up. But it some exceptional cases are there where it would not react. That is it will act as the medium for the reaction to take place — nitration reaction sulphuric acid act as the medium.