I found this VFX breakdown of the recent Superman movie to have a great explanation of what it is and what it makes possible: https://youtu.be/eyAVWH61R8E?t=232

tl;dr eli5: Instead of capturing spots of color as they would appear to a camera, they capture spots of color and where they exist in the world. By combining multiple cameras doing this, you can make a 3D works from footage that you can then zoom a virtual camera round.

I also spoke to the vfx team from Superman on how they achieved the reconstructions! (I’m also the author for the Helicopter article here).

https://radiancefields.com/gaussian-splatting-in-superman