Saba, Vin Cotto, Mosto Cotto: What is the difference?
They're basically all the same thing, although mosto cotto and saba (cooked grape must) are more similar by some explanations than vin cotto, (cooked wine) but saba is referred to vin cotto in Southern Italy, so I'm not completely sure there's that much of a product difference between cooked grape must and cooked wine; the bottom line is, the names is interchangeable and regional.
Here's a NYT link that will explain what these syrups are and offers some tips on how to use them. You may need to have an NYT account to read this link, but it's free from the New York Times:
Even more info:
Here's a quote from a CI forum poster:
"Syrup vinegar that is produced from the unfermented residue referred to as "must" that is produced from Trebbiano grapes as they are processed into wine. Fruity in flavor, Saba is a mildly sweetened vinegar that is aged for over 2 years, going through a natural fermentation process that concentrates the consistency and flavor of this vinegar as it matures and becomes balsamic vinegar. In Italian, Saba is often labeled as mosto cotto, which translates into "cooked grape juice." It may also be referred to as Saba grape mosto reduction. It is a vinegar that is typically served with meats, poultry, and desserts or combined with other sauces to enhance the flavors."
I hope this answers your question.