The sweetness of wine is just a perception. We can think that wine is sweet(off-dry),…
Tannins are from skins of wine. The better the wine, the smoother the tannins are.
The best way how to describe full body and light body taste is to imagine the difference between full-fat milk and skimmed milk.
The full fat has lovely full, almost dense feel in your mouth. The skimmed milk, on the other hand, is very watery like taste feel.