A general name for those invaders of England and Ireland who came from Scandinavia. They actually colonised quite a lot of Europe during the later Dark Ages. The Normans were really Vikings. They came over in longships and did the looting, raping, pillaging bit but then settled and had a lasting influence of much of the north of England. Look at York.
Vikings had a culture which included sagas and tales and probably boosted the story telling tradition quite a bit. They had a mythology which still has influence today (Thor and Odin are well known, as is Valhalla).
The Vikings were known as great sea travellers and traders and reached North America a long time before Columbus in open Longships.