Blank CDs serve two purposes. The first is storage. You can store a large number of files on them, and backup important files to keep them safe for years. You can also use them to make your own music CDs. You can use black CDs to make traditional CDs which will play in any CD player, or an MP3 CD which can be played in specially designed CD players. If you need a lot of black CDs, it's best to get them wholesale so you know you're getting the best prices. Before you start stocking up, make sure you have a CD burner so you can get started making your own CDs.