What is a volcano?

The word "volcano" comes from the Roman God of Fire, Vulcanus. Also the small volcanic island of Vulcano in the Eolian Islands off Sicily, was called after that god. Apparently, this island was highly active in Ancient times and people believed its crater was the chimney of the Vulcanus'forge,  where the hot lava and ash coming out from the crater were the visible evidence of his activity to forge weapons for the other gods.
On Hawai'i, the people attributed volcanic activity to the beautiful, but capricious and at times destructive goddess Pele, who loved fire and hated water.

Today, a volcano is the term for any place on the surface of the earth, where hot molten rock or magma is erupted or has been in the past.