With ballistic tracking, the faster you increase or decrease turning the throttle knob, the faster the data changes in the throttle.
When ballistic tracking is enabled, so are typematic keys. With typematic keys, when you press and hold the Y +or N - Keys, the values will continue to increase or decrease without having to do a separate key press for each increment.
With straight line tracking each movement of the throttle knob causes a fixed rate of change. When you use straight line tracking, typematic key action is off. This means that you must press each key once to cause an action.