An outsole is the bottom part of a shoe or boot. It can also be referred to as the “sole” of the shoe. Simply put, it’s the part that comes into contact with the ground. They can be made out of rubber, leather, and a combination of other materials. Some outsoles provide better traction than others, offering oil- and slip-resistance. Durable and waterproof outsoles are greatly desired by hikers and people who work outdoors and have to face the elements.