These days you can find aceto balsamico in almost any supermarket.  However what is commonly referred to as balsamic vinegar is not the same thing as aceto balsamico tradizionale, a particular condiment from the region around Modena with a long history.  The tradizionale is obtained from grapes that come from the Modena area that are crushed and then cooked to produce must.  After resting and fermentation it is put into a series of different sized barrels that, progressively, come from different woods.  The barrels are stored for proper temperature and aeration and must be aged for at least 12 years.  Within this framework there are as many different types of aceto balsamico tradizionale as there are producers.  In fact, it is not really a vinegar but a luxury product:  a thick condiment with a rich flavor balanced between sweet and bitter.  It is used drizzled on meat or fish dishes and delicious on cheese or desserts and gelato.  Commercial balsamic vinegars are a mix of must and red wine vinegar and good for salads, dressings and sauces.