In Marxist economics and its contemporary derivatives, the means of production refers to physical, non-human, inputs used in production. This includes factories, machines, and tools, along with both infrastructural capital and natural capital, the classical factors of production minus financial capital and minus human capital or labor. When used in contemporary terms, it usually applies to land or commons being converted to natural resources, and to that infrastructural capital which is not owned strictly in common but is applied to make "goods". Marx's analysis does not distinguish between infrastructural and natural means of production, but that distinction could be introduced.
Karl Marx focused on labor questions: He considered it exploitative to treat labor as just another "factor" in production, and in his analysis he chose the word "means" apparently to emphasize that labor actually acquires and applies the instructions and skills, and directly uses the tools and infrastructure - in their role as the "proletariat". The proletarians are the productive members of society, since they are the ones who must work for a living. The bourgeoisie, meanwhile, is composed of people who own various means of production, and who hire proletarians to work for them, using those means of production. The bourgeois, being the property owner, is able to extract a profit from the work of his employees by paying them less (in the form of wages) than the actual value of their products. Therefore, the bourgeois gains money (profit) for free, without doing any actual productive work. This, in the Marxist view, constitutes exploitation of the workers, and this is why they are opposed to private property over the means of production.
Marx's terms are often employed in economic analysis by socialist parties who advocate public ownership of some (or all) means of production. The affinity between labor movement causes and this advocacy is very strong - and often shared by social democrats, socialists, communists and greens. Marx's analysis in particular helped to make clear the key differences between human capital and "labor" or "human resources" - which earlier political economy favoring labor value (e.g. that of David Ricardo) had not done.
Some green economists, notably Brian Milani, draw parallels between Marx's treatment of labor and natural capital, accepting Marx's view that land is a means, but not a simple factor, of production. Others go further to argue that land, more fully regarded as natural capital must be seen as a sort of "lumpenproletariat" performing ecological work.
Still others, including many following neoclassical economics, argue that nothing that is alive (land, labor) and therefore negentropic can be counted as a "means" for anything else that is alive and negentropic - and reject the Marxist terms of reference entirely. There is thus a dispute on convergence between the idea of "means of production" and the modern general notion of capital; Marx's analysis has been important in refining the factors of production wherein individual and natural (alive, natural, creative) actors are kept separate from instructional, social, infrastructural and financial (unliving, entropic, imitative "means") "factors", at least to some degree - notably in the analyses of Natural Capitalism and some macro-economics which study the choice (by people) to do work, or take recreation.
In the analysis of Baldassari and Acquisti, any living actor may choose to use or not use a "means", but an unliving "factor" can only take orders from above, robotically, without any capacity to question. Or, indeed, any capacity to take or choose to do harm. There is thus a clear distinction between a "means", including autonomous intellectual capital, and a "factor" whose detailed choices are defined by passive instructional capital and limits of infrastructural capital. This analysis avoids however the problem of individual capital or "enterprise" or "ingenuity", and how choices to act or not act work in the large to define roles or rules.
Some theorists emphasize the "driving down" of decision-making power "closer to the customer" as making the roles of bourgeois and proletarian more alike. Whether true or false, however, this would not affect the basic idea of means of production; rather, it would simply render it ambiguous where means begin and factors end. In particular, the role of those who employ only financial capital and do not directly use the other factors of production remains distinct. The most significant feature of capitalism, in the Marxist analysis, is the fact that the ruling class monopolizes the means of protection, thus of property law enforcement, which keeps the financial capital valuable and convertible into the means of production (all other forms of capital).
There are parallels in analysis by modern feminist economists, notably Marilyn Waring who argues that women's work has been systematically devalued and undervalued, while education and training sufficient to use the "means" deemed most valuable by society have traditionally gone to men. She sarcastically parallels two very different ideas of "value" by focusing on village women in a developing nation whose day is defined by the search for clean water and dry firewood, and a man in a U.S. missile silo, whose day is defined by waiting for orders to destroy the Soviet Union. She argues, in general, that woman is to man as lumpen is to proletariat, but does not use those terms herself, evidently to avoid offending the Marxists.