A Variable Frequency Drive (VFD) is a type of motor controller that drives an electric motor by varying the frequency and voltage of its power supply. The VFD controls the speed of the motor by adjusting the frequency of the power supply. The VFD also protects the motor from damage by providing a soft start and stop. A VFD is typically used in applications where the speed of the motor needs to be controlled, such as in pumps, fans, and conveyors.