Barthes' theory states that texts can have multiple meanings and entries rather than a single authoritative one. A text can be "unraveled" through different perspectives to create new meanings. Barthes categorized texts as either "open" or "closed," with open texts allowing for unraveling and multiple meanings. He identified five codes that can be present in narratives: the action code, enigma code, symbolic code, cultural code, and semantic code. The document discusses how the opening of the film Se7en links to Barthes' theory through its use of codes like the enigma code, symbolic code, and cultural code to build tension and leave the audience questioning.