Step 1: Define the sector.
The tertiary or service sector covers transport, banking, communication, education, healthcare, tourism and IT rather than producing physical goods.
Step 2: Its weight in the economy.
It now contributes the largest share of India's GDP, driven by fast growth in banking, IT, healthcare and tourism, and it has become the biggest source of new jobs too.
Step 3: Its supporting role.
Transport, banking, insurance and marketing services help farmers and industries move, store and sell their output, so agriculture and manufacturing depend on this sector to function well.
Step 4: Its global and social reach.
India's strength in IT and BPO services has pulled in investment and exports, while wider access to education, healthcare and banking has also raised people's standard of living.
Hence, the tertiary sector matters because it leads GDP growth, generates the most employment, supports the other two sectors, and improves quality of life.