The world's population nowadays is 6.8 billion, but different regions
of the world have different population density. Population density is the
number of people per unit of area, usually per square kilometre or mile.
Commonly this rriay be calculated for a county, city, country, another territory,
or the entire world. The territory on which people live can be divided
into rural areas, urban areas and metropolitan areas. Rural areas are large
and isolated areas of an open country with low population density. The
terms 'countryside' and 'rural areas' are not synonyms: 'countryside' refers
to rural areas that are open. A forest, wetlands, etc. with a low population
density is not a countryside. An urban area is characterized by higher population
density and vast human features in comparison to areas surrounding
it. About 91 percent of the rural population now earn incomes in the form
of a salary, often in urban areas. The 10 percent who still produce resources
generate 20 percent of the world's coal, copper, and oil; 10 percent of its
wheat, 20 percent of its meat, and 50 percent of its corn. The efficiency
of these farms is due in large part to the commercialization of the farming
industry. Urban areas may be cities, towns or conurbations. Unlike an urban
area, a metropolitan area includes not only the urban area, but also satellite
cities and rural land that is socially and economically connected to the
urban core city.