In Marxism, the proletariat is a social class that did not own the means of production. Proletarians are wage-laborers who often work for/in; unsanitary workplaces, inadequate wages, and hazardous conditions are often cruelly treated and are the poorest and lowest class who own little or no property.
Within Marxist Theory, there exists a constant conflict between the proletariat and the bourgeois. For example, factory workers would desire higher wages, yet the bourgeoisie would usually/always turn them down.
According to Marxism, capitalism is a system founded on the fraudulent and underhanded treatment of the proletariat (“capitalists” are those who own the means of production.) This foul treatment takes place as follows: One - The proletariat gets employed by a capitalist and works for them; the workers then produce goods or services. Two - These products or services become the capitalist's property, who then sells them to accumulate capital. Three - A small portion of the wealth produced is used to pay the workers' share (the little they receive), while the surplus value is dealt amongst the capitalists (capital.) A portion of the capitalists' pay is used to purchase supplies, pay bills, and add more to their workforces. Hence the capitalists accumulate capital from their employees' wage-labor—the capitalists yield capital without laboring (excluding the work of hiring, purchasing supplies, and maintaining productivity.) Four - The proletariat owns no means of production; the proletariat must sell themselves daily and hourly for labor, even if it means being exploited, to satisfy the mere essentials of life. This is why Marxists argue that capitalists accumulate capital by exploiting workers/the proletariat.
Marx himself urged that the proletariat must depose the capitalist system with Socialism, transforming social planning, underpinning the capitalist system, and then evolving into a communist society in which "...the free development of each is the condition for the free development of all." (Communist Manifesto)