Hi, I'm new to wine. With red wine, what is that sharp, almost
vinegary, and to me certainly, unpleasant, taste that so many wines
have(but not all)?

For instance, I had one described as, "A Cabernet/Merlot blend, the
palate is jammy and full of fruit, with bell peppers and a little
spice on the finish." This was good on the first day.

Another, described thus, "Good berry and lightly stewed fruit
flavours, a medium body with light tannins and a fruity finish",
tasted awful right away.

thanks for your help