Quad Reproject is a technique that allows us to render sweet spot / anamorphic animations for flat display devices (TVs, Monitors, LED Walls).
It allows us to render a 3D scene from one viewpoint (camera) and map that onto multiple screens in a spacial arrangement. You might also think of that 3D scene as another convinient tool to animate content for those screens.
https://youtu.be/UBK9JD3lEM4?si=muyBYAzoQZ8DoJ_P
Lovely tutorial by B2BK is a good introduction to Quad Reproject.
https://derivative.ca/UserGuide/Quad_Reprojection