Ingredients is a type of item in Divinity: Original Sin
Many items in the world may not seem to have an apparent purpose, but they can be combined with other items in order to craft or improve potions, scrolls, arrows, food, weapons, armour, and much more.
Some books will contain recipes, but you can experiment to see what you can discover on your own. To combine or craft items, simply drag them on top of each other. Some combinations may require Crafting or Blacksmithing abilities. Creating your own skill books requires the related magical ability.
There are immovable objects, such as ovens and forges, that you may need in order to craft certain items. Drag an item on top of the immovable object to craft with it.