Reins are long, narrow straps used to control a horse or other animal while riding or driving. They are typically attached to the bit in the animal's mouth and are held by the rider or driver. By pulling on the reins, the rider can signal the animal to stop, turn, or change speed. Reins come in various materials, including leather and synthetic options, and can be designed for different types of riding, such as English or Western. Proper use of the reins is essential for effective communication between the rider and the animal, ensuring safety and control during activities.