It should also be noted that SNA theorizing encompasses two (analytically) distinct domains, which we refer to as “network theory” proper and “theory of net-works.” Network theory refers to the mechanisms and processes that interact with network structures to yield certain outcomes for individuals and groups. In the terminology of Brass (2002), network theory is about the consequences of network variables, such as having many ties or being centrally located. In contrast, theory of networks refers to the processes that determine why networks have the structures they do—the antecedents of network properties, in Brass’s terms. This includes models of who forms what kind of tie with whom, who becomes central, and what characteristics (e.g., centralization or small-worldness) the network as a whole will have.
Source: On Network Theory – Borgatti & Halgin