In this brief note, some of the frequently used concepts in the discussion of the commercial policy are explained. The purpose is to provide a ready reference to such concepts and their broad implications. We begin with the concepts of Nominal and Real Effective Exchange Rates (NEER and REER) used frequently in the exchange rate policies. In the first section we also discuss various concepts of the Terms of Trade. The Tariff policy and concepts related with it are then discussed in the second section. In the third section, the concept and implication of quota and tariffication of quota are discussed. In the fourth and the last section, we review the concept of the Effective Rate of Protection.