Active recovery is done after you have trained the muscle with heavy and complex movements.It's an advanced technique used by professional where muscle is put back to work after 2-3 of the training,but with simple movements,ex. If you have trained back on Monday,now on Wednesday you can start with 40-50 pullups of different variations before starting the actual workout.This will help pump more blood into the muscle which will aid in the recovery,by infusing more nutrients into the muscle to repair and bluid the tissue.
This method should be used at an advanced level,this technique is basically used by athletes to prepare for the shows.
It can also be used for an advanced level gym enthusiast.It is used to break the plateau.
Plateau is the condition where your body saturates and doesn't respond to your usual workout and diets.At this moment you have to be smart,and be able to break through it by using different style of methods and diet.