Terpenes are the aromatic compounds that give cannabis its characteristic fragrance. The plant contains more than 150 diverse types of terpenes. As most marijuana connoisseurs know, terpenes also give many strains their distinctive aromas. The gassy smell of Sour Diesel sets it apart from the sweet, cherry perfume of the strain Cherry Pie. However, in nature, pungent terpenes serve many valuable purposes for the plant such as protecting it from grazing animals and encouraging pollination.