The basic idea is that all item locations in the game have their items shuffled around… so for example you never know what you’re going to find when you open a treasure chest! There are many item locations in the game beyond treasure chests, for example overworld heart pieces and NPC’s that give you items - these are all included too!
This was written and is maintained by Veetorp. A big thanks to Dessyreqt, ChristosOwen, Smallhacker and Karkat for their work - without which none of this would have been even remotely possible!