Variable definitions and state codes are available in the Data Dictionary [23 KB XLSX file].
Information is also available in the accompanying open access peer-reviewed journal article:
Balk, D., M. R. Montgomery, H. Engin, N. Lin, E. Major and B. Jones. 2019. Urbanization in India: Population and Urban Classification Grids for 2011. Data, 4(1), 35; https://doi.org/10.3390/data4010035.