The divide is described as the workers and the richer capitalists who exploit the workers. It's a class conflict/struggle.
In Marx’s words, “Society as a whole is more and more splitting up into two great hostile camps, into two great classes directly facing each other—Bourgeoisie and Proletariat.” Society’s constructions were predicated upon the idea of “base and superstructure.” The workers are the base, and the capitalists are the superstructure.
I hope this helped.
