Nothing at all.
Well, technically, if your label is on a CD, it's a CD label, and if it's on a DVD, it's a DVD label. But until you take them off the label sheet and put them on discs, they're interchangeable. Both CDs and DVDs can handle full-faced labels (labels with a hole diameter of around 41 millimeters) and non-full-faced labels (labels with a hole diameter that"s typically 15-22 millimeters).
Printable discs (CDs and DVDs that you can print on directly, instead of sticking a label on) are a different matter, obviously. But paper labels can serve interchangeably as either DVD labels or CD labels.
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