AAC: Advanced Audio Coding. AAC is a lossy audio compression format used in the Apple iPod, iPhone and iTunes music store.
FLAC: Free Lossless Audio Codec. FLAC is a lossless audio compression format. One of its advantages is that it reduces the file size of an audio program from 30 to 40% (the amount of storage space it takes on a disc or other device) without sacrificing audio quality.
MP3: MPEG-1 Layer 3. MPEG stands for Moving Pictures Experts Group, an organization that develops standards for coded audio and video programs. MP3 is a lossy audio format and bit rates for MP3 music files range from a low of 32kbits/s up to 320kbits/s.
PCM: Pulse Code Modulation. Also known a Linear PCM, it is the standard audio format for CDs. PCM audio is an uncompressed, lossless storage system.
WMA: Window Media Audio. WMA was developed by Microsoft as a competitor to MP3 files and is a lossless compressed audio format.
WAV: Waveform. WAV audio files are similar to PCM audio and can be coded as compressed or uncompressed lossless audio. WAV files are similar to AIFF audio files used on Mac computers.