competing audio formats

There are a number of different file types wandering around here under the general guise of MP3 files.

• MP3 is the generic term used for audio files transmitted over the internet. MP3 files will play on computers and any MP3 player - iPods and others.
  
  
• AAC is a copy protection format used by Apple. Reportedly it offers more compression and better sound quality than MP3. iTunes music is sold in AAC format and will play on computers with iTunes software and iPods. AAC files will not play on non-iPod MP3 players unless you crack the coding.
  
  
• WMA is the Windows equivalent to AAC. It will play on computers with Windows Media Player and other audio software and non-iPod MP3 players like Creative, SanDisk, etc. You can buy music from Napster, MusicMatch, Walmart, etc. that will play on these players.
  

There are also some competing formats out there from companies trying to promote their own digital rights management options. For the time being, I'd steer clear of Microsoft Zune and Sony MP3 players if you are looking at downloading audiobooks and/or if you want to buy music from stores other than Zune and Sony. Sony, for example, says that their MP3 players will play WMA(non-DRM) and AAC(non-DRM). That won't work for anything downloaded from music stores on the internet.