It is a training session that each players have turn to do the attack and defence.
I think every team do similar sessions in training.
Where are Liverpool's problems every game? They are in defence, so training should be concentrated around defending properly as a team. The defenders should be made to learn the basics of strong defending instead of messing around doing flicks and tricks in the attacking box.
Can you not see how massive a problem our defending is? Does conceding 3 at Watford, 2 to Hoffenheim, 2 to Sevilla, 1 each to Newcastle and Burnley, 5 at City not bother you at all?