Wine decanters and aerators serve a similar purpose. Both allow wines to aerate by forcing air to circulate through the wine though an aerator is used to quickly allow the wine to breathe as it is being poured and a decanter is a leisure resting vessel for the liquid to remain without changing its tasting properties.
Young vintage wines need to be decanted for a longer period than older vintage wine blends because of the change in taste as it sits. Older wines generally have more sediment which greatly affects the taste and aroma. When you pour older wines into decanters it allows the sediment to settle in the container and not rise to taste bitter. Therefore, after pouring wines into a decanter it is best to let it sit for a while to mix with the air for a smoother tasting drink.
An aerator will allow wines to expand and take in more oxygen allowing an aromatic change and softer tasting tannin flavor. A simple aerator will achieve this purpose for a better aromatic and richer tasting red or white wines. Individual aerators are designed to allow the right amount of air mix with your favorite drink and to be poured immediately into your glass with a smooth rich finish.
With modern aerators and decanters, there is a marriage of the two for more joyful bouquet and flavor. Aerators can now be placed inside decanters so that its contents can be poured through it to be mixed with extra oxygen, which lends itself to an immediate tasteful delight.