Washers are small, flat discs typically made of metal or plastic, used in various applications to distribute the load of a threaded fastener, such as a screw or bolt. They help prevent damage to the surface being fastened and can also provide a better seal in plumbing applications. There are different types of washers, including flat washers, spring washers, and lock washers, each serving a specific purpose. Flat washers are used for load distribution, while spring washers provide tension and help maintain tightness. Lock washers prevent loosening due to vibration, making them essential in mechanical assemblies.