In Death of a Salesman, what action takes place on the apron of the stage?

Death of a Salesman's author Arthur
Miller originally wanted to entitle his landmark American tragedy The Inside
of His Head to reflect the time shifting from present to past of the
protagonist, Willy Loman. In his original conception, Miller envisioned "an enormous
face the height of the proscenium arch that would appear and open up, and we would see
the inside of a man's head"; the action of the play, therefore, would take place
exteriorly and interiorly.  Circumstances intervened and Miller
changed both the title and the staging of the play. Despite this change, however, the
play still contains two types of time and action: real and remembered. This time
shifting is the locus for Willy's tragic downfall. And it is still reflected in
the staging of the play. Miller uses both the Shakespearean stage and the modern
proscenium to symbolize the time shifting in Death of Salesman.
Events in the present take place on the domestic set framed by the proscenium, but
remembered events take place on the apron and the forestage. It can be said, therefore,
that Miller not only reconfigured the idea of tragedy, he also reconfigured stage time,
allowing it to symbolize the interior and exterior realities of the principal
character.