Knitting balls are a type of yarn used in knitting and crocheting. They are usually made of wool, cotton, or synthetic fibers, and come in a variety of colors and sizes. Knitting balls are often sold in skeins, which are large loops of yarn that can be unraveled to create the desired length of yarn. Knitting balls are an essential tool for any knitter or crocheter, as they provide the necessary material for creating garments and other items.