Italy is the largest wine producer in the world. Not only Italian wine is exported around the world, but it is also very popular in Italy.
If you want to understand the variety of Italian wine, you must understand the difference of between each region in Italy. Italian wine reflects the different cuisines between each region in Italy. The Italian wines most famous around the world are Brunello di Montalcino, Barolo and Barbaresco. There are more than 350 "authorized" grapes and more than 500 other documented varieties in circulation.
There are lots of sources where you can find information on wines in Italu. You can find information on several international and Italian guides and the most famous one in Italy is Gambero Rosso.