What are the different file formats compatible with an mp3 player?

Answer:

AA - Used by Audible.com mostly for audio books and talk radio programs.
AAC - Advanced Audio Coding, created by Dolby Laboratories, used in iPods.
FLAC - Free Lossless Audio Codec, an open-source format that uses a compression algorithm designed to use the least amount of compression possible.
MP3 - (MPEG) Motion Pictures Experts Group Layer 3, widely used format found on the web.
OGG - Ogg Vorbis is an open source format, not as widespread as AAC, MP3, or WMA. Probably the best sounding format no one has heard of.
WAV - AIFF - Uncompressed audio found on most standard audio CD. WAVs are found on Windows - PC's, while AIFFs are found on Macs.
WMA - Windows Media Audio, Microsoft's format. Most MP3 players support WMA.