Primary Sector
The primary sector of the economy can be classified as the "extractive" industry. These include the industries that produce or extract raw materials. Farmers are an example of primary sector workers, as food items are collected as raw materials, such as wheat and milk, are taken from the farm and made into other products such as bread and cheese. Other industries include the mining industries, such as coal, iron ore or oil, which extract the raw materials from the ground that will be converted into other useful items.

Secondary Sector
The secondary sector of the economy is comprised of the manufacturing industries. The manufacturing industries take raw materials and produce products. For example, the steel can be used to manufacture cars. Carpenters take wood and make homes, furniture and cabinetry. Not all manufacturing companies manufacture a complete product. Semi-manufacturing companies produce parts to be used in other products that have several stages of production, such as automobiles.

Tertiary Sector
The tertiary sector of the economy is the service industry. Service companies do not provide a physical good like the primary or secondary sectors do, but they still provide value. For example, banks, insurance and the police all are examples of the service industry. Industries included in the primary or secondary sectors will typically have employees that provide tertiary services such as advertising, accountants and warehousing employees.

(i) Primary Sector (or Agriculture sector). It includes all those economic activities which are connected with extraction and production of natural resources, e.g., agriculture, fishing, mining, etc.

(ii) Secondary Sector (or Industrial sector). It includes all activities which are concerned with the processing materials which have already been extracted at the primary stage, e.g., the mining of iron ore is primary industry, but manufacture of steel is secondary industry.

(iii) Tertiary Sector (or Service sector). It is concerned with providing support services to primary and secondary sector and includes transport, banking, insurance, warehousing, communication, advertising, etc. It facilitates smooth flow of goods and services in the economy. Importance of tertiary sector has been observed in the last decade and its contribution to GDP has also risen.