The center of gravity on a golf club refers to the place where all the points of balance on a golf club intersect. It's a really important feature of a golf club, as the center of gravity -- often just called CG -- helps determine how easy it is to create ideal launch conditions for a golf shot.
What does center of gravity do for a golfer, and where is it located?
On a driver, most golfers will benefit from a center of gravity that's low and back, meaning it's situated closer to the sole and back of the crown of the driver. With this CG position, a golfer is able to hit the ball higher with more backspin, meaning it'll be more controlled and more likely to stay in play.
However, some better golfers want a more forward center of gravity while keeping it low, so as to keep that point near where impact happens and lowering spin. That creates some more distance and potentially more roll with an accurate drive.
If you're a golfer struggling with keeping the ball from slicing, moving hard to the right, with your driver, then you may want a driver with a center of gravity that promotes more of a draw. Several manufacturers make drivers with a draw-bias center of gravity, meaning the center of gravity is moved toward the hosel of the club so it's easier to promote a closed -- or at least more square -- clubface at impact.
On irons, most golfers again want a low and back center of gravity to help them get the ball in the air and flying farther. However, better players may want a set of irons with a progressive center of gravity, getting lower as the numbers get lower. On short irons, the center of gravity would be a little higher to correspond with where the ball will be struck.
With wedges, the center of gravity will tend to move these days in a progressive fashion. As the loft increases, the center of gravity moves higher because the golf ball will more frequently be struck higher up on the face, particularly as a chip or pitch shot is hit from rough and slides up the face at impact.
How is the center of gravity determined in a golf club, and how can you change it?
The center of gravity is entirely determined by the mass properties of a club. In other words, where the weight is concentrated in a golf club determines the center of gravity position. The more weight placed low and back in a club, the lower and further back the center of gravity will be.
Changing the center of gravity position, then, is a function of moving weight where you want the center of gravity to be. That can be done in many modern drivers by shifting weights on the sole. It's possible with some fairway woods and hybrids.
Generally speaking, you can't move the center of gravity on irons and wedges.