Leeks are a type of onionlike bulb that is commonly used in cooking. They have a mild onion flavor and are often used as a substitute for onions in recipes. They are a member of the Allium family, which also includes garlic, onions, and shallots. Leeks are a popular vegetable in many cuisines, particularly in European and Middle Eastern dishes. They can be eaten raw or cooked and are often used to add flavor to soups, stews, and other dishes.