Chillin' is one way to talk about relaxing. It implies a slightly more social activity than 'progressive relaxation' - which tends to involve lying or sitting very still while you focus on relaxing each group of muscles in turn. Total relaxation means relaxing all the muscles and all the mental muscles into a sort of 'blissed out' state.
There are other ways to relax.
There is the kind of relaxation a skier feels at the top of the hill. There is the kind of relaxation the manager feels as work clicks into place. There is the kind of relaxation that comes when you are totally engrossed in a new place or a single activity.
Relaxation does not always mean loud or soft, fast or slow, still or moving.
So what does it mean? What if you could be 'just chillin' while you did your very best work?