the resource-based view of the firm (Barney 1991), posits that the internal resources of the firm are a source of competitive advantage to the extent that they are rare, inimitable, valuable and causally ambiguous. there is an assumption that firms compete on assets and capabilities that are unique and inherently internal to the firm. It is the bundle of resources that enable a firm to gain and sustain superior performance. Key concepts include resource heterogeneity ie competing firms possess different bundles of resources which are scarce and non-substitutable, and resource immobility ie resources are difficult to move across firms. The resources enable the firm to develop and implement strategies that have the effect of lowering a firm's net coats or increasing net revenues beyond what would have been the case if the resources had not been used to develop and implement these strategies.