Sugar and Home Brewing

This guy's got it right.  I'd add, however, that he has only touched on the basics.  There are many other forms of sugar available to the brewer than just the ones he mentioned.  Maple syrup, honey, and fruit juices are all popular choices, and they contain the sugars he mentions.  There also unfermentable sugars like lactose, which add body and mouthfeel to your beer when used in proper amounts.  I've only got a few minutes, but I'll expand more on this next time!