Have you ever bought a wine in a tasting room but once you get home and uncork the bottle it just doesn't taste the same? One of the leading causes for this is not enough aeration.
Hefty, age-worthy wines that may initially seem too young and tight often benefit from some time in a decanter. Although these types of wines ideally would be slowly exposed to oxygen by many decades of cellar aging, not everyone has the time or the patience to wait around to drink these impressive bottles (especially us!)
Decanting a young wine is often necessary to allow the otherwise harsh tannins to soften and become less severe. The exposure to air tends to soften up this tannic structure, enhance a wine’s aromatics, making wines that may be considered a bit shut down or closed, more immediately accessible. This is what it means to allow a wine to "open up" or "breathe".
If you aren’t sure whether this applies to the wine you’re planning to serve with dinner, there’s a simple test: Pour yourself a taste. If the wine in your glass seems a bit too tight or is off putting by the firm structure of its tannins, then try pouring it into a decanter. Not
only are the results likely to surprise you, but it can be fascinating
and fun to taste the wine at various stages as it opens up and develops over the course of several hours.