Definition - What does Porto mean?
Porto is the official name for Port wine which is exported to the United States. Using the name "Porto" helps to eliminate any confusion with port-style wines made within the US. It is required to be somewhere on the label. However, Port wine sent to England to be bottled and then shipped to the US does not need this labeling.
WineFrog explains Porto
"Porto", along with "Oporto" and "Vinho do Porto" are all recognized names for Port wines that originate from Portugal.
Porto is a traditional fortified wine made in the region of the Douro Valley and other northern provinces in Portugal. It is a sweet, fortified, red wine made from the grapes of Tinta Barroca, Tinta Roriz (Tempranillo), Touriga Francesa, Touriga Nacional and others.
The wine is fortified with a distilled grape spirit in order to stop fermentation and fortify the wine before all the sugar is converted into alcohol. The result is a rich and bold wine with around 20% alcohol content. Furthermore, it can be made into a couple of styles; Ruby Port or Tawny Port.