CD-ROM/XA

CD-ROM/XA stands for Compact Disc Read Only Memory/eXtended Architecture, a specification developed by Sony, Phillips and Microsoft, that enables many different types of data -- Audio, Video, Compressed Video, and Graphics -- to be stored on a single CD-ROM.
For example, you could have 300MB used for CD-DA Content, with 400MB used for an ISO 9660 Data Segment.