Simply put, "decanting wine" is pouring wine from the wine bottle into another container. Two reasons for decanting wine is to remove sediment from the wine you are drinking and to aerate the wine. Aeration of wine helps the acidity, sugar and alcohol to become balanced. This is commonly referred to as "allowing the wine to breathe". Red wines that have been aged for years, have a build up of sediment. Sediment, or potassium bitartrate (commonly known as cream of tarter), is formed during the fermenting process of wine making and settles to the bottom of the wine bottle. If the wine is stored properly, the wine bottle should be stored laying on its' side, tilted downward, so the wine touches the cork. While it is not bad for your health to drink the sediment, it may taint the taste of the wine. Better to decant. Young red wines and all white wines will not have a lot of sediment build up because of the short aging process. But, they still benefit from decanting because of the aeration that takes place during the decanting.
Before you touch the wine bottle to start to decant the wine, remember, the less you shake the wine bottle , the more sediment will stay on the bottom.
For decanting, you need: the wine bottle, a wine bottle opener, an empty container (such as a decanter), a wine glass, a towel and a light source.
Presummably, the wine bottle has been stored on it's side, so gently carry the wine bottle to the area where you will be decanting. Slowly stand the wine bottle upright, and if possible, let it stand for a little time to allow the sediment to settle to the bottom of the wine bottle. Carefully uncap the wine bottle and remove the cork. Smell the cork to make sure it's not musky or vinegary and check the cork for sediment. Take the towel and wipe the top of the wine bottle to remove any sediment or cork fragments. The next part is a little tricky. Turning the wine bottle around slowly, pour a small amount of wine into a glass, making sure you wet the entire inside neck of the wine bottle. This will remove any sediment clinging to the neck. Look for sediment in the glass. If any sediment is present in the glass, let the bottle rest so the sediment can settle to the bottom. If the wine is clear of sediment, you are ready to decant the wine. Most experts discard this first pouring of wine in the glass. Position the wine bottle in front of your light source. A widely used light source is a lighted candle. As you pour the wine from the wine bottle into the decanter, stop when you see the sediment start to come out. There should only be a small amount of wine left in the wine bottle that is full of sediment, and all the wine in the decanter should be clear.
You have just decanted the wine...salute!