The sides detect sour. The very center of the tongue detects salt and the front detects sweet. The gums mainly react to tannins. Tannins produce a gum drying sensation after you swallow the wine. Tannin is usually found in red wine produced to age.
Acidity is used to keep the wine from becoming flabby.
Body is used to describe a wine weight on your tongue, and referred to as light bodied, medium, or full bodied. The Finish describes how long the flavor of the wine lingers on your palate after the wine has been spat out or swallowed. A long Finnish is another sign of quality. Some people like to rank a wine from 1-5. I like to rank a wine against its price and use a number system for grading.