In order to preserve the natural sweetness in fortified wines, the fermentation is stopped before the yeast gobbles up all the sugar. Typically when you do this, you’d be left with a lower alcohol wine but since fortified wines are allowed to add spirits (in the form of a neutral-tasting grape brandy) the wines are usually around 17-20% ABV. Because of the high alcohol and sugar content, dessert wines are precious and meant to be enjoyed in small amounts (about 2-3 ounces) in tiny glasses. Of course, there are many more options in the dessert wine category other than just fortified wines (i.e. Sherry, Madeira and Port. Sauternes). Tokaj, late-harvest Loire Valley Chenin Blanc and many more are what you would call “naturally sweet” dessert wines. Their sugars are usually concentrated by some sort of dehydration, rather than the addition of alcohol. Find out more about dessert wines.