For an aspiring actor, "casting" is a pre-production process for selecting talent for a script. While "backroom" often has a negative connotation, it can also refer to the intense, private work done by casting directors to find the next big star.
The video opens not with a professional actress, but with a young woman—referred to only as "Jori"—who appears to be in her late teens or early twenties. She is dressed casually (e.g., jeans and a tank top) and carries a backpack, suggesting she came directly from class or a part-time job. jori backroom casting