Stage directions provide vital instructions in a play script to guide actors. They tell actors where to stand, how to enter and exit, and how to deliver their performance. The main stage directions describe the setting, a character's feelings, movements, and speech. A stage is divided into nine sections - center, downstage, upstage, right, left, downstage right, downstage left, upstage right, and upstage left - to guide actor positioning from the audience's perspective. Stage directions are crucial for proper scene staging and character performance.