(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 the manufacture of steel is the secondary industry.

(iii) Tertiary Sector (or Service sector).  It is concerned with providing support services to a primary and secondary sector and includes transport, banking, insurance, warehousing, communication, advertising, etc.

Primary, secondary, and tertiary sectors are the three main sectors of the economy.

1. Primary Sector:
The primary sector, also known as the agriculture sector, involves the extraction of raw materials from nature. It includes activities such as farming, fishing, mining, forestry, and hunting. The products obtained from this sector are unprocessed natural resources, which are then used by other sectors to produce goods and services. For example, farmers grow crops, and fishermen catch fish, which are then sold to food processing companies.

2. Secondary Sector:
The secondary sector, also known as the manufacturing sector, involves the processing of raw materials obtained from the primary sector to produce finished goods. It includes activities such as construction, manufacturing, and electricity generation. The products obtained from this sector are finished goods that are sold to consumers or used by other sectors. For example, a car manufacturing company uses steel obtained from the mining industry to produce cars.

3. Tertiary Sector:
The tertiary sector, also known as the service sector, involves the provision of services to consumers and businesses. It includes activities such as retail, banking, transportation, healthcare, education, and tourism. The products obtained from this sector are intangible services that are consumed by consumers or used by other sectors. For example, a hospital provides medical services, and a bank provides financial services.

In India, the majority of the workforce is employed in the primary sector, followed by the tertiary sector. The manufacturing sector is relatively small in comparison.

Overall, the three sectors are interdependent, and the growth of one sector can impact the growth of the others. A strong primary sector can provide raw materials for the manufacturing sector, and a strong service sector can support the growth of the other sectors by providing necessary services.