Sludgecrawler

What does this file do exactly? I know it comes with Lenny's Mod Loader etc. but I'd like to know what it does and if it is necessary for something I haven't come across yet. Finally I got all my 20+ .asi mods working on my Steam Deck RDR2 but only by deleting vfs.asi. I just can't figure out why that should work. When I start the LML it says some mods might not work without it but I haven't noticed any issues so far. Does anyone here know?