Ok so my explanation of this might be wrong but here is how i apply it to every day things. So when you are driving in a car and you speed up from a set of lights. Well suddenly the music you were listening to doesnt sound loud enough right? Well you put it up to match and your ears adjust to this new level, good for you! But then you get to where you were going and you turn off the car and when the music turns off you then realise how loud you were listening to your music. So simply put audio dynamics is understanding the audio noise around you and adjusting certain things you are listening too, so as to match the lower sounds to the noise in your environment. As an audio person you are always battling the sounds you dont want to hear with the sounds you do want to hear. Anyway random but hope it taught you something! Keep your ears open!