Originally Posted by zimbu1234
Those album covers are embedded into the mp3s or whatever audio files types you have. For example, when you buy an mp3 from itunes or another service, the album art will show. If illegally download or rip the mp3 from a CD the wrong way, you will not see album art.
The image does not have to be embedded in your mp3 files, and your mp3 files don't have to be "legal" to display album art. If you rip them yourself, or download them off the internet, you can name an image "cover.jpg" and put it in the folder with your mp3s. It will display that jpg for all of the files in that directory.