Port is a sweet red wine with about 20% alcohol and rather low acidity and tannin. Ideally a good port should have a rich spicy flavor and in spite of its 20% alcohol, taste very smooth.
Vintage style ports are very grapey. This grapiness comes from the practice of bottling these wines before they are 2 years old. Even though a vintage port is held in the bottle for a long time, it keeps its grapey flavor but in addition develops bottle bouquet, a special quality found only in bottle aged wines. It can take many years for vintage ports to become smooth if they have some tannin when they are bottled.
Tawny ports are aged a long time in wooden barrels. They tend to lose most of their fruit and the normal deep red color becomes more of an amber-hue (which gives the wine its name) and acquire a nutty character. They should be very smooth when bottled.