There’s no difference. Just what you’d expect. Some people don’t care enough to learn about how to actually use their computers. So some software will allow you to “import” photos from a “device” and then, per your request, delete the photos from the device once the import to your computer is complete. If you’re on a PC and using Google’s Picasa, your cut-and-paste technique works fine as Picasa usually will just index photos wherever they land. If you’re on a Mac and using iPhoto, on the other hand, the default behavior is to physically copy the photos to iPhoto’s specially managed directories, in which case using the builtin import function makes more sense.