Post Process Materials
Post Process Effects
The engine already features complex post processing based on a graph of post processing nodes. The Post Processing Materialscan be additionally inserted in some specific position. See Frequently Asked Questions section for r.CompositionGraphDebug to get a dump of the full graph.
The graph is actually not only doing post processing but also some parts of the lighting.
Blendables, also known as PostProcessMaterials, are Materials that can read the buffers then compose and modify them before they output on the screen. The easiest way to think of them is as a material overlay on the screen.