Raster versus vector, in one minute
A raster image is a grid of coloured pixels: photos, PNGs, JPGs. A vector image is a list of shapes with outlines and fills: SVG, EPS, PDF artwork. Vectors scale without blur and can be edited shape by shape.
Converting raster to vector means deciding which pixels belong to which shape. SVG Harbor does that per colour: it clusters the image into a palette, builds a mask per colour and traces each mask into smooth Bézier curves, deciding at every bend whether it is a corner or a curve.
Which images vectorize best?
Images with clear edges and a limited number of flat colours: logos, icons, stickers, comics, signage and ink drawings. Gradients and fine textures can be approximated with more colours, but the result gets larger and more stylised.