In The Hunger Games, the nation of Panem is divided into two classes: the very wealthy that live in the Capitol and the poor, who live in the thirteen outlying districts. This accords with Marx's idea of class structure in which capitalist society consists of two basic classes: the capitalists and the proletariat. The capitalists are the small, very wealthy class that are the owners of the means of production, and the proletariat are those who work for the capitalist class. Collins's story follows the classic outline of Marxism, in which the capitalist class grows richer and richer by more and more ruthlessly exploiting the proletariat, who are left with barely enough to survive.
Commodity fetishism means that in capitalism, commodities, things themselves, gain a magical importance and the laboring people that produce them become invisible. We can see this most fully in Panem. The grotesque and disturbing differences in wealth between the classes means that the upper class makes a fetish of, for example, the bizarre fashions they wear without having the least awareness of those who labored to make these overpriced goods. Commodity fetishism reaches its height with the Hunger Games, in which the lives of real humans fighting to the death are exploited: the children fighting are merely a source of entertainment—commodities—that the rich can metaphorically consume.
Alienation, which in Marxism primarily refers to the way people work merely for money, not because they derive pride or satisfaction from their jobs, can be seen in Katniss's approach to the Hunger Games. She is alienated from the "job," which she is doing merely to save her younger sister, and she is alienated from the decadent, coldhearted society it represents. She derives no personal satisfaction from the idea of killing others to survive but feels forced into this situation, just as a factory worker might continue in a soul-killing job because there is no alternative.