A dog leash is primarily used to control and restrain a dog during walks, runs, or other outdoor activities. It helps to keep the dog safe and prevents them from wandering off or getting into dangerous situations. Leashes also provide a way for owners to train their dogs by guiding them and correcting their behavior when necessary. Additionally, leashes can be used to manage a dog's interactions with other dogs or people, preventing aggressive or unwanted behavior. Overall, dog leashes are an essential tool for responsible dog ownership, promoting safety and well-being for both dogs and their owners.