Carbon atoms have a versatile nature to attach themselves to one another to an extent not possible for any other element. Carbon atoms can form long chains and rings containing thousands of atoms. The chains and rings can be branched and cross-linked. This versatile nature of carbon is the reason why there are millions of compounds of carbon present around us. Organic molecules are everywhere around us. These are the part of not our body but also food & medicines. Organic chemistry is vey important for technology also as it is chemistry of ink, paper, dyes, paint, gasoline, rubber and plastic. As it is mentioned above, there are millions of organic compounds around us, it becomes very important to classify them in groups in order to study them properly. Further as organic compounds play a very important role in our life, it is also important to identify and name them all. In this chapter we will study about the classification of organic compounds and their nomenclature and also about the techniques used for their purification.