When you drink red wine, you should use a three-finger cup to gently hold your cup, or someone can simply grab a cup of your feet. However, be careful not to use the palm to hold the glass when you hold it. The temperature will destroy the taste of the wine in the cup.
The brandy's cup is the opposite, because the dwarfish is the palm of the person holding the glass with the palm of your hand. With the temperature of the palm of your hand, the aroma of the brandy can be better evaporated.
While toasting, use thumb, ring finger and pinkie to hold the bottom of the cup and the middle finger to hold the cup. Put your fingers on the connection between the cup and the glass. Fingers should be straightened as far as possible.
As for the cocktail glass, it's tapered. I think that's because in addition to drinking, we have to look at the layered colors of the wine. The temperature on the hands may destroy the proportion of different wines. So we must make tall, champagne glasses slender. The cup body is of course used for watching bubbles.