What “vectorize” actually means
A raster image stores a colour for every pixel. A vector image stores instructions: “move here, draw a curve to there, fill it purple”. Vectorizing means working out those instructions from the pixels, which happens in four stages: reduce the image to a small palette, split it into one layer per colour, trace the edge of every region, and fit straight lines and curves to those edges.
What traces well
Logos, icons, stamps, signatures, pixel art, cartoons and screen-printed designs have flat colour and hard edges, so they trace cleanly. Photographs and gradients do not: they become thousands of tiny shapes. For those, SVG is the wrong format and a WebP or AVIF will be smaller and better-looking.