Spinnakers are a type of sail used in sailing boats. They are typically triangular in shape and are used to increase the speed of the boat when sailing downwind. They are usually made from lightweight materials such as nylon or polyester and are attached to the mast of the boat. Spinnakers are often brightly colored and can be seen in many regattas and other sailing events. The term 'sails' is used to refer to all types of sails, including spinnakers.