A use-value is something that is valuable because it is useful. It can also be a measurement of the usefulness of a commodity.
According to Marx, labor-power is "the aggregate of those mental and physical capabilities existing in the physical form, the living personality, of a human being, capabilities which he sets in motion whenever he produces a use-value of any kind."
The forces of production. This is comprised of the instruments of production (tools, machines, etc.), methods of working (skills, forms of cooperation, division of labor, etc.), and applied knowledge (science, etc.).
The economic structure of society that defines people's mode of living. It consists of the means of production as well as the relations of production.
Relations between people necessary for a certain form of material production. This is comprised of the distribution of the means of production, forms of possession (collective and individual private property), and distribution of the product.