The first is a slot cut out of the side of the peg, to allow the power/throttle wire to feed through and back into the wheel. The second is the hole for the peg was tapped to M12x1.25 (12mm diameter by 1.25 mm thread pitch). This peg can screw directly onto 12mm diameter axles and does not require axle nuts to tighten down onto the frame.
To install this peg, you'll disconnect the power/throttle wire from the axle, unscrew the existing axle nut, then screw on the ebike peg, feed the wire back through the slot in the peg, and connect it back up to the wheel.