This chapter is from the book
You should create all the graphics you can right inside Flash. If this hour taught you nothing else, remember that it's always better to create graphics in Flash than to try to import them from outside.
However, there are times when you want to import graphics, such as when you have an existing graphic that would be impossible or difficult to re-create in Flash or when a graphic requires a raster file type (usually a photograph). When you're certain you want to import, there are ways to do so.