If you don’t use Time Machine, or you want extra backups, you can back up your library or purchases to CD or DVD using iTunes. To reduce the number of discs needed for a backup, iTunes can perform incremental backups (only items added or changed since the last backup), or back up your iTunes Store purchases only.

To burn a DVD, your computer must have a SuperDrive. Some third-party DVD burners may also work.

To create backup CDs or DVDs:
1. Choose File > Library > “Back up to Disc.”
2. Select your options, and then click Next.
3. Insert a blank disc (CD-R, CD-RW, DVD-R, or DVD-RW).
4. Click Back Up.
   
   iTunes burns the number of items that fit on one disc, and then asks you to insert subsequent discs to continue burning the remaining files. Don’t eject a disc while a backup is in progress.

To restore backed-up files:
1. Insert a backup disc.
   A dialog appears, asking if you want to restore. To replace files in your iTunes library with files from the disc, select “Overwrite existing files.”
2. Click Restore and follow the onscreen prompts.

Programs purchased from the Audible website are not backed up.
Discs you create using the iTunes backup feature can be used only to restore; they can’t be played in a CD or DVD player.

Source: Apple iTunes Help