When you need this
The client has a logo — as a 400-pixel PNG from an old website, and the print shop wants vectors. A signature needs to go on documents at any size. An icon exists only as a screenshot. Tracing rebuilds these as true SVG paths: each colour region becomes an editable, scalable shape, not pixels.
The honest scope
Vectorisation shines on flat-colour artwork — logos, icons, line art, signatures, stamps, simple illustrations. It is the wrong tool for photographs, which it reduces to a posterised effect (occasionally exactly what you want, usually not). The cleaner and larger the source, the better the trace; JPEG compression halos around edges are the most common cause of rough results. After tracing, optimise the SVG and recolor it like any vector — all in your browser, with nothing uploaded.