Hideworking

Hideworking is extremely important to make your experience easier, especially if you do not trade. With leather and furs you can make clothes and tying equipment. Clothes make winter easier to survive, as they ward off frostbite. Beside, handmade clothes, with your chosen materials, is better than the shopbought. Tying equipment is essential for a lot of things like drying meat (or other methods of preservation) or for building items (like skis or rafts).

This is the second skill of choice to increase after Physician. When you need it, you need it now, not later, not after training. It's can be trained but slowly, unless you are a small game hunter exclusively.

Hideworking changes skins from butchered animals into workable leather or fur.

The two things you can do with a skin are:

Tanning
Command in game: [Alt] + J, [T] Tan the skin

Tanning 1 pound of fresh animal skin uses 0.5 lbs of water and 0.1 lbs of tanning material, either bark or fat. Butchering a carcass almost always gives enough fat to tan a hide, although you may choose to tan it with bark so that you can eat the fat.

Tanning turns the skin into leather or fur, depending on the animal the skin comes from. Fur-bearing animals:

Pig, dog and cow skin becomes leather.

Curing
Command in game: [Alt] + J, [C] Cure the skin (for preservation) This extends the life of the skin, but will not turn it into fur/leather. Curing needs water and around a day to process one skin, although it is a better idea to simply tan the skins outright.