The purpose with this system is to use the marking player's determination to mark the attacker at all time.
If CB or a backcourt player is marked, that player switches position with the wing.
If the marking player follows the following can be performed:

Example:
LB is marked and switch place with LW.
The marking player follows and become defending R1.
CB receives the ball and attack against the defending R2
The marked LW runs in and the marking R1 follows.
By doing this the defending R2 will be blocked by her own R1.
LB runs behind the mowing LW, receives the ball from CB and shoots.