This is actually a bit of information about Balsamic Vinegar. In the US the prevalent belief is that it is a single type of liquid. I'd like to introduce the beauty of the many faces of ‘aceto balsamico tradizionale’.
There are two kinds of Balsamic Vinegar. Fake: made of white vinegar and brown sugar; and Real: vinegar that has been aged in a wooden cask for decades.
Fake: There is nothing wrong with using the fake stuff. It costs much less the real deal, and it will be a uniform consistency about on the level of vinegar with a bit of sweetness added to it. Most recipes don't make a distinction and if they don't, the fake is fine.
The real stuff is unique. It is called ‘aceto balsamico tradizionale’ in Italy and is made from the musk of the grape. Depending on how long the vinegar has been aged it can taste very, very different. It must have been aged for at least 12 years to be called balsamico and at that age it tastes remarkably similar to white vinegar. The best of the vinegars are between 25 and 150 years old. Beware! The price goes up as the age goes up! You can empty your savings to have that dessert! (More than US$500/bottle)
You can identify the real thing because it will always have the number of years it has fermented. There will always be a red seal as well, proclaiming it to be the ‘aceto balsamico tradizionale’.
You may find one or two real deals in a grocery store, but they're more likely to be in a gourmet shop.