This is a resource pack that contains the lang entries for the custom advancements and banners added by YUNG's Better Dungeons (Forge) (Fabric).
This is NOT the complete mod YUNG's Better Dungeons, and this will not do anything without also installing it.
If you have a server w/ Better Dungeons and you don't want to require players to also have the mod on their client, then they can simply use this resource pack so that the advancements added by Better Dungeons will have proper names.
If Better Dungeons is used server-side only and players don't use this resource pack, then they will see stuff like "betterdungeons.advancements.root.title", but if they instead have this resource pack installed then they will see "YUNG's Better Dungeons".
This resource pack is optional, and is not required for Better Dungeons to function as a server-side only mod. It only makes it so that players can see proper advancement and banner names.