Note: This study guide offers summary and commentary for Chapter 1, Section one; Chapter 4; Chapter 6; Chapter 7; Chapter 10 and Chapter 14, all from Volume One of Das Kapital, or, in English, Capital.
Karl Marx's Capital can be read as a work of economics, sociology and history. He addresses a myriad of topics, but is most generally trying to present a systematic account of the nature, development, and future of the capitalist system. There is a strong economic focus to this work, and Marx addresses the nature of commodities, wages and the worker-capitalist relationship, among other things. Much of this work tries to show the ways in which workers are exploited by the capitalist mode of production. He also provides a history of past exploitations. Marx argues that the capitalist system is ultimately unstable, because it cannot endlessly sustain profits. Thus, it provides a more technical background to some of his more generally accessible works, like The Communist Manifesto.
This study guide focuses on one component of Capital, Marx's schema of how the capitalist system functions. Marx argues that commodities have both a use-value and an exchange-value, and that their exchange-value is rooted in how much labor-power went into them. While traditionally people bought commodities in order to use them, capitalists use commodities differently. Their final goal is increased profit. Therefore, they put out money and buy commodities, in order to sell those commodities for a profit. The cycle then repeats itself. The reason why the capitalists are able to make a profit is that they only need to pay workers their value (how much it takes to keep them functional), but the workers produce more than that amount in a day. Thus, the workers are exploited. The capitalists are able to do this because they have more power, and control the means of production. Furthermore, the workers' character is negatively affected by the system. They don't own the products of their labor, and the repetitive work they have to do makes them little more than machines.