Bowling refers to a series of sports or leisure activities in which a player rolls or throws a bowling ball down a lane. In indoor bowling, the target is usually to knock over pins. In outdoor variations, the aim is usually to get the ball as close to a target ball as possible. The indoor version of bowling is often played on a flat wooden or other synthetic surface, while outdoor bowling the surface may be grass, gravel or a synthetic surface. The most common types of indoor bowling include ten-pin, nine-pin, candlepin, duckpin and five-pin bowling, while in outdoor bowling, bowls, bocce, pétanque and boules are popular. Today, the sport of bowling is enjoyed by 95 million people in more than 90 countries worldwide.