Symbolism, Imagery, Allegory
The overwhelming majority of people in the world have to sell their labor for wages in order to survive. Marx uses the term wages broadly, so his term includes salary pay, not just hourly pay. Think about that one for a minute.
But can laborers possibly work themselves out of poverty? Only in very rare cases, says Marx, and only by figuring out how to exploit the wage-labor of other workers more unfortunate than they are.
Most of the time, a wage-laborer will manage to keep just enough value from his or her labor to survive—but not enough to amass capital. In Marx's words, "[D]oes wage-labour create any property for the labourer? Not a bit. It creates capital, i.e., that kind of property which exploits wage-labour, and which cannot increase except upon condition of begetting a new supply of wage-labour for fresh exploitation."
If that laborer somehow manages to acquire property (as in capital, not as in personal belongings), it'll be by appropriating the wage-labor of others. "Property, in its present form, is based on the antagonism of capital and wage-labour" (Section2.17).
The capitalist view, as explained by Ayn Rand, for instance, is that the wage-laborers should not be antagonistic but should instead feel grateful to the capitalists for being job creators. Marx would answer that in an economy where everyone's basic needs—food, clothing, shelter—were being met, the workers would be able to produce and keep the fruits of their labor as they see fit, rather than being forced to go to work under conditions where they are exploited and alienated.