Purfling
Those little decorative lines
Purfling is a decorative inlay that runs around an instrument, but not at the very corner edge. It lies inboard of the edge, as on this violin:
Violin purfling is a three layer line of black-white-black fiber or wood inlaid parallel to the outside, around 1/4" in from the edge.
On fretted instruments, the purfling is usually just inside the "binding" which is inlaid on the corner edge:
Here, the purfling is a wood marquetry inlay in a herringbone pattern.
This guitar has purfling around the top, consisting of black and white lines and abalone inlay. It also has black and white purfling on the side as well:
Here's a cross-sectional view of the binding and purfling of a Taylor guitar, style 610:
One could argue the point that the side purfling is actually part of the binding, but that's a waste of energy in my opinion.