It usually is because if you were eating a sweet dessert and went to drink non-dessert wine, the wine could taste sour or bitter compared to the dessert you are eating. So, usually dessert wines are sweeter.
there can be up to 150kcals in dessert wine. (3oz glass)
Dessert wine do not need to be aged, but can be. Make sure if it is a white dessert wine, it is chilled.
Ice wine, a sweet wine produced from frozen grapes, has a short shelf life similar to other dessert wines--approximately six to 18 months.
A wine cellar
muscato
There are many places where one could purchase a dessert wine. One could purchase wine a local liquor store or a grocery store like Giant Eagle or Acme.
Port.
Wine can be stored in a fridge.
Sauternes is a very sweet dessert wine, so you could use Muscat de beaume de venise (also a dessert wine), some sherry or a sweet liqueur.
No, truffles are either a dessert or a thing that European pigs find. Wine can be said to have the flavor of truffles.
Wine can be stored in a jar.