This is actually white wine vinegar. Wine vinegar is what you get when wine is exposed to the air, and bacteria get in that transform the alcohol into acetic acid. So it becomes vinegar. By the time they've done their work, there is no alcohol left. It's all turned to acid.
This is a problem for home winemakers. When you've put the going-to-be-wine into a big jar with some yeast to ferment, that takes some weeks and if you don't keep the vinegar flies out with their bacteria, you'll end up making a big jar of vinegar. So what you do is stopper the jar with a fermentation trap containing a sterile liquid to keep the flies out. I remember Dad doing this. It has the other advantage that you can tell when the wine is finished! - fermentation produces carbon dioxide gas as well as alcohol, so when the gas stops going blup blup blup out through the trap, you know it's stopped and you can bottle it.
And that is why you can buy wine vinegar when you're not old enough to buy wine - no alcohol in it.