Sometimes, when hunting animals, you'll receive an animal bone. This is a somewhat common extra drop that most land animals will give you when skinned. Think of bones in Resynced as a secondary currency, used to purchase additional land animal skins in general stores.
This is important because, as Edward, you’ll require the aforementioned skins to increase your combat abilities through the crafting menu. You’re also able to use bones to purchase the much larger sea animal bones. These are just as valuable, and also needed to upgrade crucial parts of Edward’s kit, including his maximum health capacity.
These purchases can get pricey, too. Some skins in particular can cost you three bones each. Considering that a bone isn’t guaranteed to drop from every hunted land animal, you’ll find yourself doing lots of hunting to secure the bones and skins needed to continue your journey in Resynced.