"Act One" is the initial section of a play or screenplay, where the main characters, setting, and conflict are introduced. This part establishes the groundwork for the story, providing essential background information that helps the audience understand the context. In Act One, the protagonist's goals and challenges are often presented, setting the stage for the unfolding drama. Key relationships between characters are also developed, which can foreshadow future events and conflicts that will arise as the narrative progresses.