Raster to Vector is the process of taking a Raster image and converting it into a Vector to edit in Designer and Trace.
A Raster is a Bitmap image (JPEG, PNG, GIF, etc.) that is made up of a grid of Pixels, such as a photograph.
A Vector is a drawn graphic path which is defined by a Start and End point, which may contain other Points, Curves, and Angles, drawn in Trace.