When a course has a paved cart path, the golfer should keep the golf car on the paved cart path at all times - unless he or she knows that it is OK to drive the golf cart off of the path. (Ask about cart path rules when you check in at the course; also see our golf cart rules and etiquette primer.)
A cart path can impact the playing of the game. A golf ball that hits a paved cart path on the fly might take a wild bounce; a golf ball that rolls onto a cart path might keep rolling for quite a ways (for good or bad).
And a golf ball might come to rest on a cart path, or in a position where the cart path interferes with the golfer's swing or stance. In those situations, the golfer is entitled to move the ball by dropping at the nearest point of relief, although there may be circumstances when the golfer chooses to play the ball off the cart path rather than move it (for example, if the nearest point of relief from the cart path turns out to be in the middle of a bush, you'll probably want to play from the cart path).