What Allen has mentioned is a type of servo controller that combines the advantage of stepper motor and servo motor. Unlike a stepper motor which is an open loop system, this type of servo is a closed loop system with encoder feedback but the loop is closed at the driver and not at the controller.
An ordinary stepper driver translates the pulses it receives into rotating electrical phase current to turn the motor. But the stepper driver does not know if the stepper motor ACTUALLY MOVE the required number of steps. Slippage can occur which means that there is always a possibility that the stepper motor is off position but the controller does not know about it.
For an intelligent servo, the servo accepts the pulses and directional signal from a stepper controller (such as the PLC's stepper output) but make sure that the motor DO turn the number of steps that it receive by check on the position feedback from an encoder.
Regarding your LCD display with funny characters, we would like to check with you for your configuration. Please email us your contact number to support@tri-plc.com so that we can call you for more detail info about your setup.