You will see most people referring to "motor driver" the power stage of system, and "motor controller" the logical part that control the motor driver ....
the motor controller control the motor.... but it cannot supply enuff current to the motor as it is logic type.... so it(motor controller) need motor driver to supply the current for him(motor controller).....
there are some motor controller with the driver, built-in with the controller itself
but if you use this type of device you have to replace both controller and driver each time the there's an overload on the driver circuit !...