Tannins are a group of chemicals known as polyphenols which bring an astringency to the taste of wine. They are obtained from the skins, pips, and stalks of the grape and are therefore generally only present in red wine where the grape juice remains in contact with these elements. The taste is recognisable by a slight numbness or dryness in the front of the mouth and along the gums and side of the tongue. Tannins are important because they are antioxidants which means they allow the wine to age and, as it does so, they break down and add complexity to the flavour. Think of them as the fuel of the wine.