For those of you who are interested,

An HDRI file is a 32 bit image that contains Exposure Values like those from a camera. The Background node is able to utilize those Exposure Values.

Here is a list of HDRI Cycles tutorials that I found.

https://hdrmaps.com/blog/blender-hdri-setup/

https://www.maketecheasier.com/hdr-environment-lighting/

https://www.creativeshrimp.com/hdr-lighting-in-blender-part-5.html

https://meshlogic.github.io/posts/blender/rendering/nodes-correct-hdri/

They all use the same technique. VinceBanga's SuperShaders setups same technique for Poser.

Not all HDRI files are created the same. Some contain more exposure values than others. Also, HDRI lighting is not the easiest to master but they can provide a high quality light source.

The following render was created with only an HDRI file in the Background node as the light source.