The way in which your club contacts the ball essentially determines where your ball will go.  If your club face doesn't contact the ball square then your shot will not be straight.  Professionals can hit the ball in different ways to put spin on the ball which creates a fade or draw shot which will have a slight bend to it in either direction.  If there is too much spin on the ball it will result in a slice or hook shot which will usually end up to far to the left or the right and not on the fairway.  Spin can also be useful for a golfer's short game in which he or she may want the ball to roll a certain way when landing on the green.  Putting proper spin on the ball is an aspect of the game that takes plenty of practice and is hard to do for many amateur golfers.  In order to achieve maximum distance on the drive, a golfer must hit the ball square and with maximum force.  "During a collision between the ball and a driver, peak force applied to the ball can be as high as 17 000 Newtons." (hypertextbook.com)