There are four fundamental traits that comprise a good wine. They are Acidity, Tannin, Alcohol and Sweetness.
For a wine to be considered “good,” each of these traits must be in proper proportion to each another.
This is because each of these four fundamental traits play a vital role in how the wine tastes. If there’s too much of one part, the wine will be off. And, if there’s not enough of a specific component, the wine will be lacking.
Too much acidity will make a wine taste sharp. Too much tannin will make the wine overly astringent. Too much alcohol and the wine will yield a burning sensation in your throat. And, too much residual sugar will make a wine overly sweet.
More specifically, the "hard" components of acidity and tannins typically are used to balance the "soft" components of sweetness and alcohol.
It’s truly is a balancing act for winemakers.
And, a balanced wine is one in which all the fundamental traits work together in harmony.