HRV data is a measure of your body’s stress level, which is a way of measuring your recovery from your previous workouts and your readiness to do a prescribed workout.
Because HRV is a measure of your readiness, VP adjusts (or doesn’t) your workout based on your HRV.
If your HRV indicates a high readiness score, then your VP plan doesn’t change. If you have a low readiness score, VP will change your workout to a rest day. If you are somewhere in the middle, VP will either reduce the volume or the intensity of your workouts based on your score.