Ruins of Lindisfarne Priory which was raided by Vikings in January of 793. Note the proximity of the sea to the place where monks lived and worked. Photo by David Albans. Copyright, David Albans, all rights reserved. Provided here as fair use for educational purposes.
Vikings were Scandinavians who sailed from their homelands to explore - and sometimes to settle (be sure to activate "fly" to "view" this virtual-tour animation) - other territory. Their sturdy ships (which you can virtually build) took them to places which they could raid and plunder. Monasteries, with their treasures, were favorite Viking targets.
We know about Viking raids in Britain, France and Ireland because terrorized monks wrote about them. Their accounts - like The Annals of Clonmacnoise - survive, influencing modern understanding of who the Vikings were and what they did.
Archeological evidence confirms that Vikings also traveled to North America. Scholars now believe that these Norsemen were the first Europeans to explore that continent. From their settlement in Greenland, they sailed south to a place we know as L’Anse aux Meadows in Newfoundland. They called the land they discovered "Vinland the Good."
You can virtually follow their voyage, see their reconstructed sod homes, examine pictures of artifacts they left behind and learn about their writing symbols - called Runes - by examining these links. And, thanks to NOVA on-line, you can write your name with Viking symbols.
A.D. 787. This year King Bertric took Edburga the daughter of Offa to wife. And in his days came first three ships of the Northmen from the land of robbers. The reve  then rode thereto, and would drive them to the king's town; for he knew not what they were; and there was he slain. These were the first ships of the Danish men that sought the land of the English nation.
793 A.D. In this year fierce, foreboding omens came over the land of Northumbria, and wretchedly terrified the people. There were incredible whirlwinds, lightning storms, and fiery dragons were seen flying in the sky. These signs were followed by great famine, and shortly after in the same year, on January 8th, the ravaging of heathen men destroyed God's church at Lindisfarne through brutal robbery and slaughter; and Sicga died on February 2nd. (Anglo-Saxon Chronicle, Anne Savage translation.)
The Gospels had no ordinary journey on that trip. While fleeing the Vikings, the monks - and their books - were shipwrecked in the Irish Sea. Later, the Lindisfarne Gospels washed ashore and were taken to Durham.
How, in the eighth century, were Vikings able to build seaworthy ships which took them on journeys to England, Scotland, Ireland and Wales (including the island of Anglesey)? And, parenthetically, what does the word "Viking" actually mean?