There are four basic taste areas of the tongue: sweet, sour, salty and bitter. You taste sweet at the tip of the tongue; sour and salty at the sides, and bitter at the very back of the tongue. What you want to do most times is round out the taste, so that all areas of the tongue participate equally in “tasting something.”
If a dish tastes too sour or salty (on the sides of the tongue), you can add sugar so that the tip of the tongue has something to taste as well, and the overall taste becomes more balanced. This works better with sourness than with saltiness; oversalting is very hard to compensate for.
Sourness is always an acid of some kind: sour milk, which is acidic; lemon; etc. It can be described as being sour, tart or tangy.
Be careful when salting soups, stews and sauces. As they cook, the liquids evaporate and concentrate the flavour — and the salt. It’s better to adjust the taste of such dishes for salt at the very end of cooking.
Some now say there is a fifth taste as well, which they call “umami”, which is savoury or meaty tastes, which can be stimulated by condiments like soy sauce or additives like MSG.
Our supply of taste buds starts to decrease after about the age of 45.