Training in agreements between defender and goalkeeper.

Without the attackers knowing, the defender and goalkeeper makes an agreement about who is covering which part of the goal.
In the shown example the agreement is, that the defender covers the grey area and the goalkeeper can now focus on shots in the opposite area.
That means, that the defender must not put her concentration into the blocking of the shot in total, but must focus on that fact, that no shot can be made in that area, she covers.