The document defines and describes the tertiary economic sector. It begins by defining the tertiary sector as the service sector, which includes activities where people offer knowledge and time to improve productivity through services rather than finished goods. It then discusses the importance and growth of the tertiary sector in India due to increases in population, agricultural/industrial development, and rising incomes. The document goes on to classify and describe key tertiary activities like trade, transport, communication, services, and tourism. It concludes by noting that the tertiary sector now accounts for about half of India's GDP and employment.