Post ProcessingEffects such as Bloom and Glare that are applied after a scene has been rendered. Passes provide a view of the post-processing effects in the scene. If the Post Processing node is enabled and a post-processing effect is applied in the scene, the Post Processing render pass negates these effects and separates it from the main pass. You can also specify whether or not to include the environment in the post-processing pass.
Figure 1: The Post Process pass can combine with the original render of the scene