Commodity fetishism is the observation that through many small separate acts of market exchange we command each other to behave in very specific ways, while disclaiming this same power and attributing its commands to blind necessity.  It’s a key concept in Marx’s critique of capitalism (he devotes a whole section to it in Capital),  and Marxists should understand that Marx used the term “fetish” to argue “commodities behave like little gods in that they seem to command men” and not “consumerism is immoral and vulgar.”
Fetish (noun): 1. An object that is believed to have magical or spiritual powers, especially such an object associated with animistic or shamanistic religious practices. 2. An object of unreasonably excessive attention or reverence. 3. Something, such as a material object or nonsexual part of the body, that arouses sexual desire and may become necessary for sexual gratification. 
The term commodity fetishism objectively should bring to mind the way economic actors, both rich and poor, declare themselves powerless before the pressures exerted by the world of commodities (“I’m sorry I have to fire you, but the market told us your services aren’t needed”). It’s conceptually quite similar to Adam Smith’s much-celebrated liberal notion of “the invisible hand of the market,” but rather than benevolent and wise Marx invites us to see this system as a sinister cult. The term commodity fetishism was never meant to scold people for liking material things; it’s not meant to generate guilt after the realization that one craves certain consumer goods (“I’m so bad, but those new shoes sure look pretty”). 
Commodity fetishism describes the objective fact that in capitalism we don’t generally relate to each other as humans asking each other to do things, but rather indirectly command each other through commodities. If I go to a restaurant, I don’t beg the cook to make me a meal and the waiter to deliver it, nor do I imperiously threaten them with violence, nor do I cajole them into it. I just buy the meal. The meal itself then appears to command them to move, like a little god! And I in turn must similarly follow the commands of commodities in order to acquire the money to purchase such meals. This is how the factory comes to want to be used, and how the tropical fruit comes to want to find its way to Stockholm.  As Marx puts it:
To [producers], their own social action takes the form of the action of objects, which rule the producers instead of being ruled by them. 
From this perspective, one of the central tasks of communists is to liberate workers not from work or desire itself, but from a generalized lack of decision-making agency in the face of crude economic fetishism. People should decide what people do, not commodities! Looking for alternatives to enslavement by commodities, some look back to feudal, religious, and romantic patriarchal forms of despotism,  but socialists look ahead, towards socialism’s multidimensional interaction and negotiation, demotic and democratic. 
Consider the following Hegel quote. It predates Marx by many years, but it’s actually very related to commodity fetishism:
Since the man of common sense makes his appeal to feeling, to an oracle within his breast, he is finished and done with anyone who does not agree; he only has to explain that he has nothing more to say to anyone who does not find and feel the same in himself. In other words, he tramples underfoot the roots of humanity. For it is in the nature of humanity to press onward to agreement with others; human nature only really exists in an achieved community of minds. 
Capitalism also “tramples underfoot the roots of humanity.” With the advent of fully-developed commodity production, labour-power itself becomes a commodity.  And so in capitalism all of social life becomes a series of inscrutable and non-negotiable orders, given and received passive-aggressively, reducing us to a materially, intellectually, and socially impoverished state of being, subservient to markets and without recourse. As César Vallejo put it, “the word — the most human of all social relations — has thus lost all of its essence and collective attributes.”  Democracy? “Vote with your wallet!”
The confusion that reigns over fetishism is both widespread and very understandable. The original meaning is antiquated and, frankly speaking, its origins in establishing spiritual hierarchies between religious traditions is kinda racist. Meanwhile, the more Freudian meaning of the term — the “sexual fetish” — is super popular and very intuitive. That said, it produces a wrong understanding of commodity fetishism. We should endeavor to correct this misunderstanding, since the alternative interpretation transfigures Marxism into a monastic doctrine of pious asceticism that — putting aside any of its moral merits — is very unappealing. Marx was very confident that such a project would never grip the masses and lead them to struggle and triumph over capitalism. The slaying of a fraudulent and tyrannical market-religion, though? We’d sign up for that.
 “A commodity is a mysterious thing, simply because in it the social character of men’s labour appears to them as an objective character stamped upon the product of that labour; because the relation of the producers to the sum total of their own labour is presented to them as a social relation, existing not between themselves, but between the products of their labour.” — Karl Marx, Capital Vol. 1., “The Fetishism of Commodities and the Secret thereof” (1867). [web]
 The Bojack Horseman song “Don’t Stop Dancing” is sung in the voice of the commodity-fetish that is show business, saying, effectively, “the show must go on” no matter what that means for the people making it. [web] — N. F.