Light Screening = ?

Slowly getting into the hobby and been lurking for a while to pickup some advice from the site. Been focused on L1, but curious about other options. I know that screening means different things to different people, but I've seen the term "light screening" referenced a lot.

For someone focused on limiting RW information disclosure, what does Light Screening really mean providing?

Thx!

2 legit/verified/current references. No hair or blood samples necessary