A rest-pause method where one long activation set is followed by several short mini-sets with about 5 breaths of rest between them.
Borge Fagerli's method. Take a set to roughly 1 to 2 reps in reserve, for example 15 reps at a weight good for 17. Rest 3 to 5 deep breaths, do 3 to 5 more reps, rest again, repeat for three or four mini-sets, then stop when the reps drop below the target.
The point is efficiency. Because the muscle stays close to failure the whole time, nearly every rep after the activation set is an effective rep, so 15 plus four mini-sets of 4 gives a lot of hard reps in about three minutes.
Use it on isolation and machine work where fatigue is local. It is a poor fit for squats and deadlifts, where the limiting factor is breathing and the lower back rather than the target muscle.