The idea behind class systems is an important concept linked with urban sociology. Metropolitan areas have a distinct social class system: an upper class, a middle class and a lower class. Each class has its own characteristics. Upper-class people tend to have a big home, lots of money and a high-paying job. Middle-class people tend to have an average-paying job and do reasonably fine with finances. Lower-class people tend to have very little money, live in poor housing conditions and work in unskilled labor jobs.
Community is another important concept behind urban sociology. Communities are groups of people who interact together in an environment. Communities organize around a set of shared values. The study of urban sociology deals mostly with the experiences of communities rather than the structural setting or formation of communities.
Another concept behind urban sociology is urbanization, which deals with the idea of physical growth in urban areas that global changes have brought about. The United Nations defines "urbanization" as the movement of people to urban regions from rural regions. In the report "2007 Revision of World Urbanization Prospects," the U.N. estimated that half the world's population would live in urban areas by the end of 2008.
The concept of space deals directly with urban sociology in that space can be very limited in urban settings. In urban environments, thousands of people may be living within a square mile of one other while more rural environments have far fewer people living in close proximity. A person's "personal space" is defined as the region around a person that he regards as psychologically his. A person may feel discomfort, anxiety or even anger if someone invades his personal space. Access to personal space can be very limited in urban environments.