Leather and wool are the two fabric types that are most commonly made of animals. There is a big difference in how they are made, and whether or not they are humane to the animal. Leather involves taking the skin of the animal from the hide, and dying it with various colors and chemicals to make it weatherproof. This means it often comes from dead animals.
If an animal - such as a cow, a horse, or even an eel - is being raised for its meat, the skin is often sold to leathermakers. Wool, on the other hand, is made from sheep, alpaca, and llama furs. The fur can be cut off of the animal without hurting it. It’s a more humane alternative to leather, and is much cheaper because it can be easily regrown and made again and again.