A dry wine is not at all sweet. Its main components are crisp and a bit tart. A dry wine is good to cook with and often makes a great combination to spicy foods. A dry wine is simple and subtle in is flavors. It has a neutralizing effect on foods and the palate.
It means, basically, that the wine is not very sweet. With a dry wine, all of the sugar has been fermented into alcohol, so there is no sweetness really left in the wine.