"For Us Men and For Our Salvation"

In the Nicene Creed, the phrase "Who for us men and for our salvation came down from heaven" turns our attention from the person of Christ in relation to His Father as the eternal Son of God, to the work of Christ in relation to us as the Lord Jesus Christ - the eternal Son made flesh. This work of Christ for us takes place in two states of His incarnation in human flesh: His Humiliation and His Exaltation.

What does it mean that this work is "for us"?