Physiography is the “stage” on which every other chapter of Indian geography plays out. Rivers, climate, soils, forests, minerals and even population density follow the lie of the land. That is why UPSC keeps returning to it.

What UPSC asks

Prelims: location-based facts — which range lies where, the order of Himalayan ranges from north to south, Bhabar–Terai–Bhangar–Khadar, passes of the Western Ghats, the channels between islands, and which hills belong to the Eastern Ghats.
Mains (GS I): origin and significance of the Himalayas, contrast between the Western and Eastern Ghats or between the two coasts, and how relief shapes agriculture, settlement and disasters (land subsidence, landslides, coastal erosion).

The six physiographic divisions

Division	One-line identity
The Himalayan Mountains	Young fold mountains on India’s northern rim
The Northern Plains	Alluvial plains of the Indus, Ganga and Brahmaputra
The Peninsular Plateau	Oldest landmass; part of Gondwana
The Indian Desert	Sandy, arid land west of the Aravalis
The Coastal Plains	Narrow western plain, broad eastern plain with deltas
The Islands	Andaman and Nicobar (volcanic/tectonic), Lakshadweep (coral)

Start with the core page on the physiographic divisions, then revise with the quick revision sheet and test yourself on the practice questions.