It's an Electric Parking Brake. A motor applies the brakes to the rear wheels. It also provides Hill Start Assist and Hill Start Hold. For confidence I would practice a Hill Start on a quiet road a few times.
It has to be better than the Vauxhall Handbrake which was famous for failing if your brake discs were hot when you parked.
When parking on a hill leave the car in gear and slightly angle the wheels towards the kerb. I read that somewhere recently.
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