Final answer:
The string or lace used for fastening shoes is known as a shoelace. It is threaded through eyelets on the shoe and tied in various ways to secure the shoe on the foot.
Step-by-step explanation:
The string or lace used for fastening shoes is commonly referred to as a shoelace. The purpose of a shoelace is to hold the shoe securely on the foot by threading through a series of holes, loops or eyelets on either side of the shoe opening. These laces can be made from a variety of materials, including leather, cotton, and synthetic fibers, and they come in different lengths and styles to suit various types of shoes, such as athletic, casual, or formal footwear. Tying shoelaces can be done in various ways, with the most common method being the bow knot.