Bowling is a target sport and recreational activity in which a player rolls or throws a bowling ball toward pins (in pin bowling) or another target (in target bowling). In the U.S. and Canada, the term bowling usually refers to ten-pin bowling; in the U.K. and Commonwealth Countries, however, the term bowling could also refer to lawn bowls. In pin bowling, the goal is to knock over pins at the end of a lane, with either two or three balls per frame allowed to knock down all pins. A strike is achieved when all the pins are knocked down on the first roll, and a spare is achieved if all the pins are knocked over on a second roll. Lanes have a wood or synthetic surface onto which protective lubricating oil is applied in different specified oil patterns that vary ball path trajectories and characteristics. Common types of pin bowling include ten-pin, candlepin, duckpin, nine-pin, five-pin and kegel. The historical game skittles is the forerunner of modern pin bowling. In target bowling, the aim is usually to get the ball as close to a mark as possible. The surface in target bowling may be grass, gravel, or synthetic. Lawn bowls, bocce, carpet bowls, pétanque, and boules may have both indoor and outdoor varieties. Bowling is played by 100 million people in more than 90 countries (including 70 million in the United States alone), and is the subject of many video games.