Making music CDs with ITunes
If you create a playable CD with iTunes, then the software converts them to a format that can be played through any hi-fi or CD player and burns that to a disc. If it was a data CD you used, then that works in a similar way to a USB flash drive, just copying the files and burning them to a CD. These will not be playable in a CD player, but you can get the files off from a computer. 
Hope this helps.