You go to a bike shop and you'll find only two kinds of bikes, right? A road/racing bike for going fast, and mountain bikes for going through the woods.
If that's what you've been led to believe, you're in for a treat. Hybrid bikes -- the fastest growing category of bikes sold -- are quickly becoming the ride of choice for people who want the best of all worlds. They've got the speed and lightness of a road bike, combined with a more comfortable upright riding position and extra durability and control of a mountain bike.
So, if you're mostly riding on paved roads or bike paths but don't want to be all hunched over on the bike like you're a racer in the Tour de France, a hybrid may be right for you.