In neoclassical economics, economic rent is any payment (in the context of a market transaction) to the owner of a factor of production or resource, supply of which is fixed.[1] In classical economics, economic rent is any payment made (including imputed value) or benefit received for non-produced inputs such as location (land) and for assets formed by creating official privilege over natural opportunities (e.g., patents). In the moral economy of neoclassical economics, economic rent includes income gained by labor or state beneficiaries of other “contrived” (assuming the market is natural, and does not come about by state and social contrivance) exclusivity, such as labor guilds and unofficial corruption.

Edit: In case anyone needs this broken down: Online videogame marketplaces are a resource. The supply of online videogame marketplaces is fixed. Valve is the owner of the largest online videogame marketplace, Steam. The publisher of a videogame pays Valve to list their game on Steam. A payment to the owner of a resource, the supply of which is fixed, is economic rent. Imagine how low you gotta be to downvote Wikipedia.