Dry wine is any wine that contains very little or no residual sugar. Dry wines typically do not have a sweet taste, due to their lack of sugar.
The dryness of a wine depends on the amount of sugar left in the final product, as fermentation causes sugars in the wine to convert into alcohol. Wine that goes through the process of fermentation with no interruptions and that contains the proper type of yeast has very little sugar left over. The result is a dry wine. Sweeter wines are created by decreasing the time allotted to the fermentation process. Shortening this process preserves some of the sugars in the wine.