iTunes Audio File Conversion to CD Playable File

For an audio CD, the conversion is automatic. Make a playlist of the songs you want on your CD. You can fit about 74 minutes of music (about 20 songs) on a 650 MB CD-R disc. Some discs can contain 80 minutes (700 MB) of music. (You can see the size of the selected playlist at the bottom of the iTunes window.) Right click on the playlist and select "Burn playlist to Disc (or use the iTunes File menu > Burn Playlist to Disc. When the Burn Settings dialog appears, select Audio CD and click "Burn".

If your CD player can read an MP3 CD, you can store more than 12 hours of music, or about 150 songs, on a 650 MB CD-R disc. (You can see the size of the selected playlist at the bottom of the iTunes window.) Your playlist can contain only MP3s. You can convert your AAC songs to MP3 as explained here: How to convert a song to a different file format, http://support.apple.com/kb/HT1550

Use the iTunes Help file to search for burning CDs and DVDs for more info.

Once a file is compressed, it can't be uncompressed. What iTunes does is convert the AAC format songs to the Redbook Audio CD Format so that your CD player can read the disc. If you insert the burned audio cd into your computer, a Mac will see the songs as AIFF files, while a windows PC will see the files as .cda files. Any quality lost in compressing the files to AAC cannot be restored, but the iTunes store standard AAC/256 kbps files are reasonably close to an uncompressed AIFF file and are satisfactory to all but the most demanding audiophile.

BTW, Apple has developed a Disc Burning Quick Assist document here: http://support.apple.com/kb/HT1152