Seam piping is a decorative addition to a seam where thin pieces of material rolled into tubes around cords are sewn within the seams, creating a protruding pipe of material along the seam line.
Long piped side-seams are characteristic of western boots, hessian boots, and other horse riding boots, sometimes in colors contrasting with that of the uppers.
Terminology
Some makers use “piping” specifically to refer to fabric and “beading” specifically to refer to leather. Others use the terms interchangeably.
Consider being specific about what material you mean whenever addressing someone who routinely handles both leather and fabrics.