Minecraft wiki entry for Graphics_setting, associated text: currently Java Edition centric - Bedrock Edition differences need to be researched
"reduces the amount of visible rain or snow" according to its description as of 1.18.1 - demonstrate?
darkness vignette presence - MC-241321
world border vignette presence - MC-54988
I've heard it affects fog rendering but don't know exactly how
it definitely affects or affected rain somehow (https://twitter.com/Dinnerbone/status/527075906595340288)
any other differences I may have missed
possibly the fabulous world border bug (MC-187669). 