How does post-processing work in Unity?

Post-processing in Unity refers to the effects that are applied to a camera's output after the scene has been rendered but before it is displayed on the screen. This process typically involves the manipulation of visual elements like color grading, bloom, depth of field, and motion blur, among others.

The correct answer highlights that these effects are applied to the final 2D image, enhancing the visual quality and adding stylistic or corrective elements that can greatly influence the viewer's experience. This post-rendering stage allows developers to fine-tune the visual presentation without altering the original 3D assets or scene configurations, providing flexibility in achieving the desired aesthetic outcomes in gameplay.

In contrast, other options focus on aspects that are not representative of post-processing. For example, filters applied in real-time during rendering pertain more to the immediate rendering process rather than adjustments made after the fact. Adjustments made to 3D models before rendering and lighting effects added during the export process refer to pre-rendering stages, which do not align with the concept of post-processing.