Buttermilk tastes creamy and tangy; it is similar in taste to plain yogurt. If it tastes bitter, then it is spoiled. Buttermilk is a cultured dairy product that provides a level acidity to recipes that call for it.
Buttermilk is used in a variety of food preparations, including baking and desserts. It lends a tangy flavor to traditionally rich dishes that call for straight cream or milk. True buttermilk is the liquid product that is left over from churned milk when butter is made. It is difficult to achieve this type of milk without extra effort and there is often not enough of it to sell commercially. Instead of taking the time and effort that is required to make true buttermilk, commercial companies will cause regular milk to sour and label it as cultured buttermilk.
The taste of cultured buttermilk is similar to true buttermilk because it provides the sour acidity, but it is not able to provide the creaminess that is present in true buttermilk. Commercially cultured buttermilk can be used in recipes that call for buttermilk because the taste cannot be differentiated in a recipe. The main way that cultured buttermilk tastes different from true buttermilk is when it is being used as a drink or when it is not being cooked at all.