Cooking is the art of turning raw materials into more filling and tasteful foods. In some cases the raw materials cannot be eaten directly and must be used in cooking to be edible (such as flour and most fish). A skilled cook can make supplies last longer by succeeding a cooking check. Cooking also contains knowledge on how to prepare meats and vegetables properly with minimal waste, meaning that a successful check will provide 25% more usable meat and food from any raw material.
In addition, when cooking food, the below results will apply if you're out and about and need to get the maximum out of your rations.