The following folders are kept here:
bg (where advancements that run in the background are kept)
recipes (where advancements that grant recipes are kept)

This folder is where all of RMF's advancements are stored. Advancements in this data pack are used to either congratulate a player for completing something a bit out-of-the-way (like eating a cake), or to teach/show a player how to do something (like finding berries in grass or new fruits in trees)