It's an electronic parking brake. Those are common now because a small switch takes up less interior space than a lever for a cable-actuated parking brake, and the computer can disengage the parking brake if it detects that the driver is attempting to drive with it activated. The computer is involved in brake pad replacement to tell the parking brake motor to open to its widest position to accept new pads, and calibrate itself to their thickness.
This requires a special adapter and software subscription rather than a button on the infotainment screen because Hyundai is engaging in rent-seeking and perhaps trying to direct business to its dealers.