In general, the class created by these conditions is an urbanized underclass. This happens as people come to the cities in search of work. If they cannot find work, or if the work does not pay well enough, they end up poor and, often, living in shanty towns.
El Salvador has not had as much of this as other countries like, for example, Brazil. El Salvador's industrialization was not as robust as other countries' and so there was less to draw Salvadoreans to the cities.
Even so, urban growth did happen and did create an underclass living in shantytowns.
El Salvador has a long history of two primary class distinctions: Upper class consisting of the wealthy coffee growers and the workers who grow the crops as well as the people who have been moved out of their environments due to urbanization. With the industrialization of cities a middle class developed and this has been further supported by loans from the World Bank. At the same time persons indigenous to the forests and other areas that have become urbanized have been forced to dwell in a society in which they have little skills This process has created a lower class in the city creating the stratus layers of Upper, Middle, and Lower class citizens.