Natrone is very on the spot with these answers. I just wanted to throw in a
couple of websites that might help if you want some more information:
http://www.bjcp.org - These are the people that judge beer festivals and
whatnot. The information here may be very technical.
http://www.realbeer.comhttp://www.beeradvocate.com
Both those last two sites are a little more end-user friendly.
modnar