Amarone is produced in the region of Veneto by estates that make Valpolicella, one of the most popular wines of this area in Northeastern Italy. The same grapes, primarily Corvina (usually the leading component in the blend) along with Rondinella and Molinara, are used to produce Amarone. But the difference between the two wines is usually striking; where Valpolicella is a medium-weight wine meant for consumption with lighter fare with in its first 3-5 years, Amarone is a much more robust wine that is perfect with game birds or other such sturdy fare over the course of 7 to 15 years.
The reason for the stylistic difference in these wines is in the winemaking. To produce an Amarone (properly known as Amarone della Valpolicella Classico), a winemaker will take the harvested grapes and lay them on a straw mat, often in an attic or other warm room. The grapes then dry over the course of several months creating a raisiny flavor that is a distinctive character of Amarone.
As Amarone comes from the Italian word amaro ("bitter"), most examples have a tartness or slightly astringent edge to them. Alternatively, you may notice a sweet edge to them that can be explained in the concentrated sugars the grapes pick up during the drying process. Certainly, the combination of raisiny and sweet black fruit can make Amarone an irresistible temptation.
That slightly sweet edge in the finish can also come from the fact that a particular Amarone may not be entirely dry. Amarone is actually a recent innovation, dating back only from the 1950s. Before that, the process of drying grapes in this fashion (known as appasimento) resulted in a sweet, super-rich wine known as Recioto. Legend has it that the first Amarone was a mistake, as a winemaker had let a barrel of wine ferment too long and the wine's residual sugar had been eliminated. Recioto is still made today and its sweetness and richness make it a perfect choice at the end of a meal, often with powerful cheeses.