Quick answers at PeterWhieldon.co.uk
Good question! Aftertaste is detected by your nasal passages and the back of the throat.
Sometimes separately and sometimes simultaneously.
Some people often refer to ‘a lingering finish’ where the taste stays with you for some time (if you give it time before taking another sip).
So ‘aftertaste’ is simply the taste that stays on your tongue after you have experienced the initial taste.
Many wines, and spirits, have two distinct tastes… the initial taste and the aftertaste. As an example, Irish Creams have an initial taste of the whiskey, followed by the aftertaste of the cream… and how lovely that is!!