Decanting, on the other hand, is when you gently pour an older wine into another vessel for the purpose of separating the wine from the sediment that has collected in the bottle. Most people prefer not to find dark flakes and grains swirling around in their wine.
I personally prefer to pour the older wine gently from the original bottle into the glass and skip the middle step of using a decanter. The chances of losing delicate aromas in an older vintage wine increase with each additional step you put it through.
Hoosier Wine Guy