In the context of this question, region refers to a specific geographic area or locality that is being studied. It can be as small as a neighborhood or as large as an entire country.
Related terms
Geographical area: A defined space on Earth's surface that has distinct boundaries such as countries, states/provinces, cities/towns.
Demographics: Statistical data relating to the population and particular groups within it (e.g., age distribution, gender ratio) in a given region.
Census: An official count or survey of the population conducted by government authorities for statistical purposes.