The three main models of urban growth and land use differ from one another largely in where they believe the various types of land use will be located within an urban area. There are three main theories. These are the concentric zone model, the sector model and the multiple nuclei model.
In the concentric zone model, the urban area is made up of concentric circles emanating from the city center. In the middle of the urban area would be the central business district. Outside of that would be light manufacturing. Outside of that would be low class residential areas followed by middle class and upper class areas. The final ring would hold commuter areas.
This was modified by the sector model. It held that transportation routes would mean that the various zones would not be circular. There would be a central business district (CBD), but the manufacturing areas would radiate in wedges from that district along major transportation lines. The CBD and the manufacturing areas would be adjoined by low class housing. Outside the low class housing would come middle class housing. There would be a wedge of high class housing going out a major transportation route.
Finally, there is the multiple nuclei model which envisions a number of central districts. There will be a traditional CBD, but then there will be secondary business districts further away from the CBD. Low class housing will cluster near the CBD and near manufacturing areas. Middle and high class housing will cluster near the outer business districts.
Thus, the models differ in where they think various kinds of land use will be located. Please see this link for graphic representations of these models.