The phenomena of power swapping between unequal parallel linear waveguides is well known [18]. When the medium is nonlinear, the light induces an axially nonuniform structure. A simple qualitative description of nonlinear couplers exist [47] for a medium with an arbitrary dependence on intensity. It requires knowing only the familiar modes of the axially uniform linear coupler. This qualitative description displays the physically meaningful parameter of power in each core, and does so pictorially in two-dimensions. It also gives a clear physical interpretation of stability and bifurcations. Furthermore, these results for the cw case are qualitatively similar to those for soliton switching. Finally, the method was also first to predict the switching properties of triple core couplers [49].