While torque has other meanings outside of golf, for the sake of the sport the term applies to a golf club shaft's ability to resist twisting. This twisting will no doubt have an impact on the distance and accuracy of one's shot. Torque can also be thought of as a force that leads to rotation within a golf club, or a measure of approximately how much twist there is in a particular club.
Higher v. Lower Torque
For the purposes of golf, shafts with lower torque are typically of higher performance and provide more forgiveness in terms of accuracy. Meanwhile, those clubs with higher torque tend to features less accuracy. Flexible shafts are known for having higher torque, due in part to their increased ability to bend.
Torque and Swing Positioning
For those golfers who are right-handed, check the position of your knee upon completion of a shot. If your left knee is parallel to your toes, this is ideal. However, if the knee is out above the toes, this means too much torque (force) might have been put into the shot, and over time this can result in knee injuries. Meanwhile, if the knee isn't far out enough to be parallel with the toes, this means not enough force was put into the shot. This usually results in an incomplete swing.
Torque and Flex
The flex of a golf club shaft is the energy stored during the downswing, upon which it is released at the point of impact. This flex is directly correlated with torque, in that the more a club can flex the better it can rotate around its axis (which, in essence, is the definition of torque). Of course, the more flex there is in a golf club, the more torque--and in all likelihood-- the less accuracy and forgiveness on a golf shot.
Golf Clubs and Torque
For those who tend to slice their shots, selecting a shaft with some torque is ideal as it will result in more squaring up of the club head at the point of impact. On that note, it might be best to purchase a graphite shaft over a steel shaft, as steel has very little torque. As a rule, the bigger the slice, the more torque necessary to square up shots.
Meanwhile, those who tend to hook their shots should choose a club with very little torque, as it will keep the club head squared up. On that note, it might be best to choose a steel shaft in this instance, as steel has very little torque.