Means of labor include machines, tools, plant and equipment, infrastructure, and so on: "all those things with the aid of which man acts upon the subject of labor, and transforms it." (Institute of Economics of the Academy of Sciences of the U.S.S.R., 1957, p xiii). Those means of production participate in the process of exploiting labor for surplus value. Subject of labor is the material worked on.
Means of production is sometimes confused with factors of production. The term factors of production is typically understood as an explanation for income as duly paid to owners of each means of production and also to the workers themselves within capitalism. By comparison, the term means of production applies to these means independent of their ownership and their compensation, and regardless of whether the mode of producing is capitalist, feudal, slave, group labor|communal or otherwise.
This term has been more simply described as the resources and apparatus by which goods and services are created. In an agrarian society it is the soil and the shovel, in an industrial society, it is the mines and the factories.
There are two subtle but important points to the Ownership of the Means of Production. The first being that owning the Means of Production is not the same thing as owning physical property, nor is it equal to owning money. Rather OMP refers to a cultural practice in which a few individuals within a larger corporation (or company) control and decide what is done with the entire profit created by that corporation. If one were to define the word "Corporation" as a particular kind of "group of people" then to later say that a few select individuals "own the corporation" then, by substitution, one must be saying that those select individuals own the group of people. In any case, this apparent paradox only arises when one confuses the owning of property with the owning of a corporation. When keeping these two kinds of ownership separate, the paradox of "owning people" evaporates.
The conclusion ultimately reached is that while the "owners" of a corporation only contribute a tiny fraction of the total labor and time in creating profit, they have complete control over that profit and how it is used. The practice of OMP in human societies is then a type of game where some people are labeled owners (Marx used the term, Bourgeoisie) and other people are labeled workers (Marx used the term, Proletariat). The bourgeoisie have complete control over both how the proletariat are paid in wages and complete control over how the profit from production is used, thus giving rise to a class division.
Contrarian interpretations of this practice might state that wages paid to workers are subsumed under the regular costs of maintaining business. However, Marx considered it a reification to treat labor as just another "factor" in production; it implied an inversion of means and ends, so that people were effectively used as things.
Marx's terms are often employed in economic analysis by socialists who advocate public ownership of some or all of the 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 capital and "labor".
Marxists define economic systems in terms of how the means of production are used, and which social class controls them. Thus, in capitalism, the means of production are controlled by the bourgeoisie, (the "capitalists" - the owners of capital). In the pure ideal of socialism, such as that "communism" was/is supposed to be, the MoP are controlled by the workers production collectives directly. In fact this situation has only been historically realized temporarily such as in the Israeli kibbutz or the early Soviets before the entrenchment of the communist party as a "New Class", or in isolated or preliminary form such as in the final phase of the Second Spanish Republic, or various experimental utopian communities.