 “Competition” is a feature of markets, but is also used in different senses, e.g., with regard to institutional competition or evolutionary competition. In markets, competition results from the fact that agents seek to find the best deal, thus creating competition among the participants on the other side of the market, supply or demand respectively. Markets are called “competitive” when they have certain structural features that include a large number of buyers and sellers, comparable goods, and the absence of informational asymmetries. In what follows, the focus is on competitive markets, leaving aside the specific problems (in particular unequal market power) of non-competitive markets such as monopolies or cartels. It should be noted, however, that even in seemingly competitive markets there are often “pockets” of unequal market power, e.g., when a company is the only employer in a certain region or when a bank possesses more information than its customers. To the degree to which such deviations from the model of a competitive market are unavoidable – for example because network effects in the digital realm lead to highly concentrated markets – they need to be taken into account in normative evaluations of these markets.