From Wikipedia: “Balsamic vinegar (Italian: aceto balsamico) is a kind of vinegar inspired by traditional products from Italy.
The original, costly, traditional balsamic vinegar (Aceto Balsamico Tradizionale), is made from a reduction of cooked white Trebbiano grape juice, and used as a condiment. It has been produced in Modena and Reggio Emilia since the Middle Ages, being mentioned in a document dated 1046. Appreciated in the House of Este during the Renaissance, it is highly valued by modern chefs and gourmet food lovers.
Balsamic Vinegar of Modena (Aceto Balsamico di Modena), an inexpensive imitation, is today widely available and much better known. It bears a Protected Geographical Status label, and is the kind commonly found on restaurant tables and used in salad dressing.”
“Traditional balsamic vinegar is produced from the juice of just-harvested white grapes (typically, Trebbiano grapes) boiled down to approximately 30% of the original volume to create a concentrate or must, which is then fermented with a slow aging process which concentrates the flavours. The flavour intensifies over the years, with the vinegar being stored in wooden casks, becoming sweet, viscous and very concentrated. During this period, a portion evaporates: it is said that this is the "angels' share", a term also used in the production of bourbon whiskey, scotch whisky, wine, and other alcoholic beverages.
None of the product may be withdrawn until the end of the minimum aging period of 12 years. At the end of the aging period (12, 18, or 25 years) a small portion is drawn from the smallest cask and each cask is then topped up with the contents of the preceding (next larger) cask. Freshly reduced cooked must is added to the largest cask and in every subsequent year the drawing and topping up process is repeated. This process where the product is distributed from the oldest cask and then refilled from the next oldest vintage cask is called solera or in perpetuum.
Consortium-sealed Tradizionale balsamic vinegar 100 ml bottles can cost between US$150 and $400 each.”
“Commercial-grade balsamic vinegar is used in salad dressings, dips, marinades, reductions, and sauces.
In Emilia-Romagna, tradizionale vinegar is most often served in drops on top of chunks of Parmigiano Reggiano and mortadella as an antipasto. It is also used sparingly to enhance steaks, eggs, or grilled fish, as well as on fresh fruit such as strawberries and pears and on plain crema (custard) gelato. Tradizionale vinegar may be drunk from a tiny glass to conclude a meal.
Contemporary chefs use both tradizionale and condimento vinegars sparingly in simple dishes where the balsamic vinegar's complex tastes are highlighted, using it to enhance dishes like scallops or shrimp, or on simple pastas and risottos.”
“The names "Aceto Balsamico Tradizionale di Modena" (Traditional Balsamic Vinegar of Modena) and "Aceto Balsamico Tradizionale di Reggio Emilia" (Traditional Balsamic Vinegar of Reggio Emilia) are protected by both the Italian Denominazione di origine protetta and the European Union's Protected Designation of Origin.
Balsamic vinegar contains no balsam. The word balsamico (from Latin balsamum, from Greek βάλσαμον) means "balsam-like" in the sense of "restorative" or "curative".”