The cast (actors) of the play get in place on stage.
They practice where they are supposed to stand during each part of the scene, and act out a few parts of the script
In this picture, the cast is playing Rock, Paper, Scissors. Have you played this game with your friends or family?
Blocking: The precise movement and positioning of actors on a stage in order to facilitate the performance of a play, ballet, film or opera (originally planned using miniature blocks).