An eyelet is a hole that's meant for threading a cord or lace through. When you lace up your sneakers, you pass the shoelace through eyelets in your shoes.
Many eyelets have metal rings that make it easy to put strings or cords through them, while others are simply holes punched in cloth or leather. Tarps and tents often have eyelets, as do sails on sailboats. Tiny hooks, such as the ones on dresses and undergarments, are also sometimes called eyelets. The word comes from the Old French oeillet, the diminutive of oeil, "eye," or literally "little eye." The Latin root is oculus, "eye."