Golf is a club-and-ball sport in which players use various clubs to hit balls into a series of holes on a course in as few strokes as possible. Golf, unlike most ball games, cannot and does not use a standardized playing area, and coping with the varied terrains encountered on different courses is a key part of the game. Courses typically have either 18 or 9 holes, regions of terrain that each contain a cup, the hole that receives the ball. Each hole on a course contains a teeing ground to start from, and a putting green containing the cup. There are several standard forms of terrain between the tee and the green, such as the fairway, rough (tall grass), and various hazards such as water, rocks, or sand-filled bunkers. Each hole on a course is unique in its specific layout.