“Wheel arches” refer to the contoured panels around each wheel’s opening in the vehicle’s body. On many SUVs like the Prado, these include extra moulding or flare trims (plastic/ABS/styrene) to:
Protect paint/body from stones, dirt, mud thrown up by the tyres
Prevent rust or damage to the metal behind
Improve aesthetics: give a rugged, offroad‑look or wider stance
Allow for larger tyre + wheel combinations by increasing clearance or protecting body when tyres protrude more