Well first, the purpose of both aerating and decanting is to exposing wine to air. This does two things: triggers oxidation and evaporation. The combination of oxidation and evaporation will reduce some compounds while enhancing others, making the wine not only smell better but taste a lot better too.
Oxidation is what makes an apple turn brown after its skin is broken, and evaporation is the process of liquid turning into vapor.
Aeration could increases the fun of drinking wine by releasing its scent and enhancing its flavor. As a characteristic of wine, tannin adds both bitterness and astringency, as well as complexity. Aeration can soften the tannins in young winesby reducing the high level of carbon dioxide.
Some say that most red wines, but only some white wines, usually require aerating– or in wine slang – they need to ‘breathe’ right before being consumed.
Funnels/aerators are a way to aerate wine, but just opening a bottle and pouring a glass will also provide aeration, as will swirling your glass of wine. You can also pour a wine more slowly which also performs aeration to the wine.
For more extreme aeration, decanting a wine works well too. Decant simply means to pour a wine from one vessel, its bottle, into another. After a while, aerated winesbegin to oxidize, and the flavors and aromas will flatten out.
The reason you decant a wine or Port serves two purposes: to separate a wine from any sediment that may have formed and to aerate a wine in the hope that its aromas and flavors will be more vibrant upon serving. A decanter lets wine breathe, which allows certain flavors and notes to express themselves after being stuck in a bottle; wine decanters don’t have seals as whiskey decanters do. Not every wine needs decanting.
Decanting is necessary with Port wines that age in bottle versus those that age in wooden casks.
Morale of the story: you don’t need to spend top dollar on your house party wines. Decant the cheap bottles of red before your guests come over, we promise you they will taste double the price you paid!