I really struggled with this idea of deliberately playing the ball for a long time. What my mind kept picturing was the defender deliberately playing the ball to the attacker who was in the offside position. To me, that sounds fair enough. Of course, this is not in the book which states: "A player in an offside position receiving the ball from an opponent who deliberately plays the ball, including by deliberate handball, is not considered to have gained an advantage, unless it was a deliberate save by any opponent".
So, the idea goes that if an attacker is in an offside position and the defender intentionally touches the ball, in any way, as it travels from the attackers team mate to the attacker in the offside position, it's not an offside offense.