Why do we want our wines to breath?
In the simplest of terms, Wine that has had a brief exposure to airis positive since it allows wine to breathe similar to stretching its legs after being cooped up in the bottle for so many years. This exposure has a positive effect on the wine after 25 to 30 minutes. Intensely tannic or younger reds may need up to a few hours.
What is it? Its simply allowing the wine to come into contact with the air. This oxidation transfer can always be a two edged sword. Too little, you have a harsh wine, too much, and the wine may be spoiled.
Which wines? I have always found this to be true with red wines. Almost any red wine will benefit from some time breathing. Sometimes, it can be as little as 30 minutes, and with some Italian wines, I have let it breathe for over 3 hours! The major reason behind allowing wines to breathe is to attempt to tame those wild tannins.
Tannin is a textural element that makes wine taste dry. Tannin is a naturally occurring polyphenol found in plants, seeds, bark, wood, leaves, and fruit skins. … As a characteristic of wine, tannin adds both bitterness and astringency, as well as complexity.
Some wines have what I call wild tannins. They are harsh, bold and very noticeable. Its what gives you that bitterness and puckering feeling as you sip on the wine. Allowing air to come in contact with the wine, allows these tannins to mellow out. I like to describe this process as taking a wild young brat and turning it around to be a gentle aging grandparent.
There are many different ways to accomplish this breathing. I have always preferred the old fashion natural way. That is, just withdrawing the cork and letting the wine stand!
Today, in restaurants, and many home tastings, people tend to get impatient.
So there are a number of different ways to speed up this breathing process.
Carafe 
With this method, the most air can be exposed to the wine as quickly as possible. This can reduce the amount of time you normally need to let a wine breathe by almost 50%. There are so many different styles and types of carafes, but they all serve the same purpose.
Decanting is a process similar to pouring wine into a decanter, except, the purpose is to clarify or remove sediment or particles from a bottle of wine. This could have happened from a cork breaking into the bottle of wine, or from an old wine that has a lot of sediment. The sediment is not bad for you, but its appearance may turn a few people off. There is an art to decanting. You generally tilt the carafe vessel and slowly pour the wine. Always looking for any particles or sediment. Some people, use a candle behind the bottle neck, to spot particles easier. Even some people, take the lazy way out and use a cheese cloth to strain out any particles or sediment. That works, but boy, is it so much of an un-wine thing to do!
Aerators 
Once again, the main purpose is to allow as much oxygen into the wine. Using any one of the many different aerators accomplishes this. I have found that using this method, the wine that is poured into the glass feels like it has been breathing for at least an hour. So, this is a quick easy method to get those tannins tamed!
During one of my wine tastings, I ran an experiment. I had a very young Italian Montepulciano d’Abruzzo. A very harsh tannin wine to start with.
First, I poured a little into a glass and let everyone taste it and had them provide me with their responses. Most of them felt the wine was too difficult to drink.
Second, I poured some of the wine through an aerator. The people were quite amazed that the same wine tasted so much better and it was only minutes after opening the bottle.
Third, I poured some of the same wine into a carafe and let them taste it 30 minutes later. All of the people noticed the difference and began to enjoy the wine.
Still, being an old fashion wine buff from the 1960s and 1970’s, the only method I really use is
pulling the cork and letting the wine breathe naturally.