If your looking to make a back up copy of the songs in your iTunes music library, here's a quick overview of how to create the archive copy:
1) From the iTunes library, click the browse button (Edit > Show Browser).
2) Select "All" for Genre, Artist, and Album.
3) Click on any song in the list below and then click Edit > Select All.
4) Click File > New Playlist and name it "Backup"
5) Access the preferences menu (Mac= iTunes menu > Preferences / Windows= File > Preferences)
6) Click "Burning" and select Data CD or DVD and click OK.
7) Select the "Backup" playlist from the Source window.
8) Click the "Burn Disc" button. iTunes will prompt you for a CD or DVD to complete the backup. If your music library is too big for one disc, you will be prompted for multiple discs.
Once the backup is finished, remember to go into Preferences and reset the disc type to Audio or MP3, whatever your preference.
For more info, visit the iTunes homepage.