Fermented grapes are grapes that have undergone a natural process where yeast converts the sugars in the grapes into alcohol and carbon dioxide. This process is essential in the production of wine, where the fermentation can enhance the flavor and aroma of the final product. The type of grape, fermentation time, and conditions can all influence the characteristics of the wine. During fermentation, the skins of the grapes may also contribute tannins and color to the wine. Different varieties of grapes, such as Cabernet Sauvignon or Chardonnay, are used to create various styles of wine. Fermentation typically occurs in controlled environments to ensure the best results.