No, Shakespeare, I am not talking about the Guinness World Record for holding your breath. Think about a large mouth.
Decanting aerates wine or is used as a method to separate wine from its sediment. Typically red wines are the ones to benefit most from breathing before serving. However, there are select whites that will also improve with a little air exposure. In general, most wines will improve with as little as 15-20 minutes of air time. However, if the wine is young with high tannin levels, it will need more time to aerate before enjoying. Aerating might also change how a wine's alcohol is perceived. For example, you might find that with some air, a wine seems smoother and the alcohol more integrated; or if it's exposed to too much air, the fruit flavors might fade and the alcohol can stick out more.
Some believe that merely uncorking a bottle of wine and allowing it to sit for a bit is all it takes to aerate. This method is futile, as there is simply not enough surface area at the top of the bottle to permit adequate amounts of air to make contact with the wine. So what's a wine lover to do? You have two options: decanter or wine glass.
Any large liquid container with a wide opening can be used as a decanter. For pouring wine into glasses, make sure that you pour into the center of the glass with a good 6-10 inches of "fall" from bottle to glass to allow for further aeration during the actual pour.