In order to know the real mechanics of distributive structures, and particularly of their evolution, it is first necessary to identify and analyse the functions they have to fulfil and the way in which they are (or are not) fulfilled. Every retailing firm has to fulfil, well and economically, a specific set of distributive functions in order to justify itself to its partners in the marketing channel. Distributive functions are fulfilled by the retailing firm in a certain environment which conditions its marketing strategy and efforts through particular opportunities and constraints that are the exogenous marketing factors for the firm. Of course, these market variables are for the most part not under the control of the firm. The marketing strategy of the retailing firm consists in performing a certain set of distribution functions (combining them in an all particular quali-quantitative mix), taking advantage of certain market opportunities and minimising certain market constraints. For this it employs special marketing instruments (endogenous marketing factors, under the firm's control) combined in a particular "retailing mix" which is unique for that firm and that gives it a specific "differential advantage".