AAC (also known as: mp4; m4a) wiki it - http://en.wikipedia.org/wiki/Advanced_Audio_Coding
 

license: proprietary (not owned or created by Apple, by the way, though this is default format used by iTunes), but free to distribute songs in this format
technical woo-hoo: better than mp3 at same bit rates
compatibility: Mobile: any iOS device (iPod or iPhone or iPad); Android; assorted others. Mac* &/or Windows°: iTunes*°; Foobar°; Winamp°; Musicbee°; Songbird*°; Clemetine*°; Play*; Cog*; current versions of the awful Windows Media Player (Windows 7+)° or that goofy Windows 8° music app; etc. Linux: various, if decoder installed
Library Industries encodes from lossless FLAC files using: XLD with Quicktime / Core Audio, constrained Variable Bit Rate (minimum 320 kbps)

MP3 wiki it - http://en.wikipedia.org/wiki/MP3
 

license: proprietary, but free to distribute songs in this format until Library Industries starts raking in 100 grand per year, then I gotta pull these files, or so "they" say
technical woo-hoo: weakest of these formats, but has been around the longest and plays on most everything
compatibility: see tech woo-hoo
Library Industries encodes from lossless FLAC files using: MAX with LAME, Constant Bit Rate (320 kbps)

OGG (Ogg Vorbis) official web site- http://www.vorbis.com/
 

license: Open Source! Free!
technical woo-hoo: better than mp3 at same bitrates; perhaps comparable to AAC
compatibility: Mobile: Android; various Sansa players; etc. Mac* &/or Windows°: Foobar°; Winamp°; Musicbee°; Songbird*°; Clemetine*°; Play*; Cog* but NOT Apple or Microsoft programs such as iTunes or Windows Media Player. Linux: any player in your distro's repo
Library Industries encodes from lossless FLAC files using
: XLD (based on Vorbis aoTuv) , Quality: 10 (our highest bit rate - a bonus for you Open Source types!)