City - Suburb - Exurban

Figure 17.9  Exurban Los Angeles

the community of Palm Desert currently marks the outer fringe of the Los Angeles metropolitan area.
Here development is concentrated along major transportation corridors and is surrounded by desert.

Figure 17.10  Urban Terminology

Geographers define metropolitan areas, cities, suburbs, and exurbs in specific ways.
note that a suburb might also be defined as a city if it has legally defined boundaries and a government.

After an hour of driving, the traffic thins and you pass more open spaces.
Finally, about 15 miles east of the city of Palm Springs, the strip malls,
new housing developments, and golf courses give way to the vast, 
wild expanses of the Mojave Desert ( Figure 17.9 ).

Scientists who study urban ecosystems would use more specific terminology to describe your drive.
The U.S. Census Bureau defines an area as urban
if its average population density is at least 500 people per square mile.
Certainly, the entire corridor from Los Angeles city center to Palm Springs qualifies as urban.
A city is an area that is defined by legal and political boundaries
and has a formal government and taxes ( Figure 17.10 ).
Thus, the city of Los Angeles is bounded by very precise city limits.
Within those limits, the decisions and policies of the Los Angeles mayor and city council
hold sway over its 3.8 million residents. 
Extending out in all directions from the city center is the Los Angeles metropolitan area.
A metropolitan area is a large central city and the adjacent communities that
have a high degree of social and economic integration with that central city.
The transportation system and movement of commuters
between the suburbs and the city is a very visible example of such integration.
Suburbs are the parts of the metropolitan area located outside of the central city.
Beyond the suburbs are exurbs, areas where patches of commercial
and residential development are interspersed in a matrix of rural land.

The Environment and You by Norman Christensen (2012) Pearson - 524page