Vector images are images described by shapes such as circles and squares, as opposed to bitmap images which are described by pixels - squares of color arranged in a grid.
The shapes are precise mathematical descriptions of the image and can be scaled without becoming blurry or "pixelated" (that blocky look that bitmap/raster images so often get when scaled up).
No more tedious hand-tracing
Hand tracing can take you hours more...
- Mac OS X 10.4 and later