At the end of a performance, the performers receive the applause of the audience.
How did it get to be called the curtain call?
Either the curtain has come down on the action, and now the actors are called by the audience's applause, or on a raked stage the actors are standing in front of the proscenium curtain, as far downstage as they can go, because gravity has been pulling them inexorably downwards. We in the audience applaud that none of the performers have fallen into the orchestra pit.