Industries can be classified into 1) Primary 2) Secondary and 3) Tertiary.
Primary industries include all those activities, which are connected with the extraction and production of natural resources and reproduction and development of living organisms, plants etc.
Secondary industries are concerned with using the materials, which have already been extracted at the primary stage. These industries process such materials to produce goods for final consumption or for further processing by other industrial units.
Tertiary industries are concerned with providing support services to primary and secondary industries as well as activities relating to trade.