Dynamic balancing is a way of balancing machines by rotating parts quickly and measuring the imbalance using electronic equipment. The imbalance measured can then be corrected by adding or subtracting weight from the rotating parts until the vibration is reduced.
Basically, all machines have some form of residual vibration. Enormous vibration in rotating machinery can cause high levels of noise and more importantly, significantly reduce the life of components. So, the ideal thing to do would be to remove all causes of vibration and allow the machine to run completely smooth. The process of balancing is the removal or addition of weight to the device, so that this effective mass centre approaches the true axis.