When we produce a good by exploiting natural resources, it is an activity of the primary sector. Since most of the natural products we get are from agriculture, dairy, fishing, forestry, this sector is also called agriculture and related sector.
The secondary sector covers activities in which natural products are changed into other forms through ways of manufacturing that we associate with industrial activity. It is the next step after primary. Since this sector gradually became associated with the different kinds of industries that came up, it is also called as industrial sector.
After primary and secondary, there is a third category of activities that falls under tertiary sector and is different from the above two. These are activities that help in the development of the primary and secondary sectors. Transport, storage, communication, banking, trade are some examples of tertiary activities. Since these activities generate services rather than goods, the tertiary sector is also called the service sector.
The value of final goods and services produced in each sector during a particular year provides the total production of the sector for that year. The sum of production in the three sectors gives the Gross Domestic Product (GDP) of a country.
Organised sector covers those enterprises or places of work where the terms of employment are regular and therefore, people have assured work. The unorganised sector is characterised by small and scattered units which are largely outside the control of the government.
Another way of classifying economic activities into sectors could be on the basis of who owns assets and is responsible for the delivery of services. In the public sector, the government owns most of the assets and provides all the services. In the private sector, ownership of assets and delivery of services is in the hands of private individuals or companies.