Chaptalization is the process of adding sugar before or during fermentation to boost the alcohol level of a wine. It's usually done to compensate for underripe grapes grown in cooler climes, such as those found in northern Europe. In most cases only enough sugar is added to increase the alcoholic content by 1% to 2%. It's virtually undetectable and doesn't make the wine any sweeter because all the sugar is converted into alcohol. The whole process is strictly governed by law, and is generally illegal in Italy, Germany, southern France, and California (where it isn't needed anyway).