The Primary sector includes activities related to agriculture, forestry, mining, quarrying and fishing. This sector includes all those activities which directly uses natural resources. The services in this sector are entirely dependent on the availability of natural resources in order to keep the day-to-day operations running. These activities form the base for all other products that are manufactured. An example is of a carpenter making wooden furniture.
For this Secondary activity, he will need wood as a raw material, which is obtained through the forestry activity. Similarly, jeans are made from cotton, which is provided by agriculture. This is the reason why the word 'Primary' is used for these activities.