The Blending Settings node connects to the Bending Settings pin on nodes under the Blend category of the Output AOVs (figure 1). 


Blending Settings Node


Figure 1: The Blending Settings node connected to a Render AOV output node

Blending Settings Parameters

Mode - The blend mode used to combine the background and foreground. This is only used in the region of intersection covered by both the background and foreground.

Regions - Determines which regions of the background and foreground to include, based on the two alpha channels.