India is the world’s most populous country, but its people are spread very unevenly — crowded on the Ganga plain and the coasts, thin in the deserts and mountains. Human geography explains that pattern and how people move and settle.

What UPSC asks

Prelims: Census 2011 figures (density, sex ratio, child sex ratio, literacy, urbanisation), definitions (census town, urban agglomeration), phases of population growth, types of rural settlements, functional classification of towns, and recent survey results such as NFHS-5.
Mains (GS I): factors of population distribution, demographic dividend, migration and its consequences, urbanisation and the rural–urban continuum. The social side (population policy, women, poverty) is taken up in Population and Associated Issues.

Key sub-topics

Sub-topic	Core idea
Distribution and density	Physical, economic and historical factors
Growth	Four phases since 1901; demographic transition
Composition	Sex ratio, age, literacy, religion, language, SC/ST
Migration	Streams, causes, consequences
Settlements	Rural types and patterns; urban definitions and functions

Start with Population Distribution and Settlements, then use the quick revision sheet and the practice questions.