AAC

This is an audio format that proclaims better quality audio while creating a smaller file than that of MP3. Apple's I-Tunes music store uses this for purchased music.

AIFF

This is an audio format used by Macintosh computers. It creates very large files, so it isn't suitable for portable devices.

CDA

This is the file format used for commercially produced audio CDs. This yeilds the highest quality, but creates a very large file which is not suitable for portable devices.

Ogg Vorbis

This is an open source audio format which is free for use by anyone who wishes to develope projects with it. It is comparable to other compression formats, but with no license fees accociated with it.

Real Audio

This is an audio format used by Real Player.

WAV

This is an audio format used in Microsoft Windows. It creates a large, but high quality file.

WMA

This is a format created by Microsoft. It is used by some music download services because it allows copyright protection to be built into the files.