Topstitching refers to the visible stitching that is done on the top side of a fabric or garment. It adds both decorative detail and reinforcement to the seams or edges of a piece.
In this case, black seats are combined with contrasting topstitching in red for the seats, instrument panel, doors and centre console, along with red seat belts. (mercedesblog.com)
This vest has a crew neckline with topstitch detail and brand logo on the chest. (religionclothing.com)
The navy trench with contrast white topstitch detailing features gold button epaulet and sleeve detail, two front pockets and a removable belt / tie - which can be worn tied tight around the waist, or loose and open. (theundone.com)