Essentially, yes. And unless you plan on writing your own PID loop, you can treat it as a black box that will automatically adjust the motor speed to match the setpoint.
To be honest, that's not exactly what happens. PID takes the speed or position of the motor from the encoder and calculates the difference (or error as I will refer to it from now on) from the setpoint. It uses that error to calculate how much to adjust the motor's power to meet the setpoint. PID comes from the Proportional, Integral, and Derivative terms used to control how PID calculates the setpoint. I'm not too familiar with the NI LabView implementation of PID, so I can't really tell you any more. If you want to learn more about PID and control theory, see
http://www.controlguru.com/pages/table.html