Stage directions are instructions the playwright leaves in the script for the actors, other than the dialogue. Depending on the writer's personal preference, these may be rendered in:

  • Italics
  • Bold
  • (Parentheses)
  • Just about anything else. It's generally clear from context what's a stage direction and what isn't.

Some actors or directors may chooes to ignore these directions: they are merely suggestions from the playwright on how best to perform the play.

Stage directions can tell the actor anything the author thinks is pertinent, not just blocking. For example:
GLORIA (sobbing): No, my dear! Don't leave me! (GLORIA collapses on the floor)
STEFAN is indifferent.
GLORIA: How could you be so cruel? (She hurls her book at STEFAN) I thought you loved me! Exit through upstage arch

As you may have noticed, stage directions actually often function just like emotes! So, you too can write a play: just pretend it's a chat room, and then later do a regex Find & Replace to fix the formatting.