What kind of finish is the 'self-fabric binding' mentioned in the description?

Breaking down the terms helps make sense of it. 'Self-fabric' refers to the exact same fabric as the outer shell of the garment, and 'binding' refers to a finish that wraps and covers the cut fabric edge with a strip-shaped fabric. Instead of folding it inward and stitching it down, the border is enclosed by wrapping it once, resulting in a thin line along the edge. If bound with a different color or a different material, that line stands out; if wrapped in the same fabric, the line blends seamlessly into the garment.

This garment finishes the neckline and armholes—in other words, the openings where the arms pass through—by wrapping them with self-fabric^[1]. There is a reason it is used specifically in these two places. It features a sleeveless design with a deeply scooped round neckline^[2], and a slim fit that reveals the body line^[3]. Being sleeveless with an open neckline means it is a garment where the edges are fully exposed.

hmmm, since it is a garment with nowhere to hide, even a single edge finish appears to be a detail that determines the overall impression.