When you load music into your iPod from your computer, it's stored on iPod's hard disk in MP3 or Advanced Audio Code (AAC) format. Both formats compress the original music so the files don't take up too much space. Stored along with each file is metadata that contains information about it, such as the artist name, album name, music category, and so on. This allows you to easily categorize and find music you want to play. The number of songs you can store on an iPod varies according to the hard disk size and how much each song has been compressed. With typical compression using the AAC format, you can store about 10,000 songs on a conventional iPod's 40GB hard disk.
