These links will explain the basics and then some of surround sound audio.
I suggest starting at the top and work your way down. Happy surfing.

http://www.ee.washington.edu/conselec/A95/projects/surround/surround.html
http://www.dolby.com/
http://timefordvd.com/tutorial/SurroundSound.shtml
http://electronics.howstuffworks.com/surround-sound.htm
http://hometheater.about.com/od/beforeyoubuy/a/surroundsound.htm
http://members.cox.net/surround/
http://www.surroundassociates.com/fqmain.html
http://www.audiorevolution.com/equip/surround/
http://www.microsoft.com/windowsxp/using/windowsmediaplayer/expert/bridgman_03january07.mspx