Like a novel, short story, or other literary works, scripts usually follow a narrative. The reader/viewer follows characters on some type of journey or arc, whether it be physical or mental. However, the structure of a script varies differently from your average book:
Many novels use chapters and sections to differentiate change in the story, either place, time, or character point of view. Scripts segment their narrative in a similar way, using acts and scenes.* Maggio Directing Fellow Anna Bahow explains the difference between acts and scenes:
Anna Bahow, Directing Fellow: Acts vs. Scenes
*Note: While most playwrights will use acts and/or scenes to delineate their story line, this is not true of all plays. Some playwrights will just write one long play. This is especially prevalent when all the action happens in one room.
Script Reading Basics