When and Why to Decant
Imagine living in a bottle for a few years. Not much room to breathe in there. It's only natural for a wine to need a little space to stretch out once the cork is popped. Enter the decanter.
Decanting is essentially the act of pouring a wine from one vessel to another, whether it splashes into an actual decanter or a wine glass. This brings the wine in contact with oxygen, so it can take a few deep breaths and release more layers of flavor. Pouring the wine at a slant ups the oxygen factor, bringing out more character and depth. Typically, about one to two hours of breathing time is ideal, but when time is of the essence, pouring the wine back and forth between two decanters gets the job done quickly.
Many red wines love to spend time in a decanter, but most white wines and many Pinot Noirs don't benefit very much from decanting. When in doubt, don't decant a sparkling wine. The bubbles don't appreciate the extra oxygen.