What is this workout move called and what does it work?

I saw this girl at the gym today holding a weight plate and she would have her legs straightened, and would just bend over as if she were trying to touch her toes with the weight in her hands. No squatting/bending involved. Does anyone know what this is called and what it works? I'm just really curious if it is supposed to work your butt or back or what! I'm always looking for new exercises to do :)
What is this workout move called and what does it work?
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