Your palate confirms your nasal impressions. It increases the temperature of the wine and carries out work that is quite simply physical and tactile, focusing on two very important notions: the complexity of the wine and above all its balance. Complexity gives an indication of aromatic richness, of the scope and the persistence of the aromas. Balance measures the relationships between the different savours in the wine. A wine’s "savours" refer to a set of tactile impressions that the mouth is capable of liking or not liking: acidity, astringency and sweetness are the main ones.
Acidity is very important as it gives a wine depth. We sense acidity on the sides of our tongue. Without acidity a wine is flat and uninteresting and its cellaring capacity is jeopardised. On the other hand, too much acidity makes wine a bit aggressive – we say it is "green".
Unctuousness compensates and balances acidity. This purely physical sensation comes from alcohol, sugar or glycerol. The top of the tongue identifies sugar. Southern wines are generally more unctuous than those grown in northern vineyards. This sensation is also called roundness. It gives an idea of the texture of the wine, perceived as a whole in the mouth. A very acidic wine can be very pleasant if it is sufficiently unctuous, such as a Riesling from Alsace.
Astringency refers to roughness and informs us about the structure of the wine on the palate. This sensation is produced by tannins and depends on their toughness. Tannins block proteins in saliva and provoke an impression of great dryness, of roughness. But there are different nuances of tannin: Médoc wines have massive tannins, but they are very ripe, thanks to Cabernet Sauvignon; Beaujolais reds on the other hand have fewer tannins, and they are more delicate, which is typical of Gamay grapes, emblematic of the terroir. These wines are more feminine, but cheeky because slightly pear-drop-ish.
Because pleasure is an overall sensation, the important thing when tasting is the balance between these three dimensions. Aromatic complexity does the rest, i.e. it makes the difference between a good wine and a classic.