Cooking is a mechanic in The Long Dark that the player can perform over any Fire.
The primary purpose of cooking is to take raw meat and fish the player either finds or collects, and turn it into cooked meat. Cooked meat is not as caloric as Raw Meat and won't fill the Hunger bar as much, but the condition of cooked meat improves, and it will rarely cause Food poisoning, whereas raw meat will almost always make the player sick.
The player can also warm up cans of food such as Tomato Soup. This will not change the calories of the food, but it will make the food hot, and eating hot food will give the player the Warming up condition, as well as restoring a chunk of the Cold meter.
The secondary purpose of cooking is to melt snow and make Unsafe Water. The player can further this by either boiling the water over the fire to make it Potable Water, or using Water Purification Tablets to make the water safe.
Because the player must stand close to a fire when cooking, all the secondary effects of a fire happen to the player. The Cold meter will increase, and Wolves will be scared off by the flames while the player cooks.