I read about candies that have "fondant" in the middle used as filling - what is it? Are there other uses for it?
There are two types of fondant: poured and rolled.
Poured fondant is sugar and water that has been cooked to the soft-ball stage and then beaten until creamy and opaque. If you've ever had a Cadbury Creme Egg, the filling is fondant.
Rolled fondant is the icing commonly used on wedding cakes. It is also used prominently in cake baking TV shows, such as Ace of Cakes. It too is primarily sugar and water, but it also has gelatin, glycerin, and glucose to thicken the sugar but keep it pliable.