Why would my daughter be applying for Universal Credit if she’s living at home?

[AutimnW1nter]

She’s has full PIP but I don’t understand what Universal Credit is for. She was advised to apply for UC.

My DS (19) has just put in a claim for UC as he hasn't yet managed to find a job. He'll be paying me some rent (board?) Taking over his phone bill and paying for his own clothes/leisure time.

What he pays me will go towards the bills and food.