Who were the vikings?

Contrary to some popular conceptions of the Vikings,they were not a "race" linked by ties of common ancestry or patriotism, and could not be defined by any particular sense of "Viking-ness" most of the Vikings whose activities are best known as Denmark, Norway and Sweden, though there are mentions in historical records of Finnish, Estonian and Saami Vikings as well. Their common ground and what made them different from the European peoples they confronted was that they came from a foreign land; they were not "civilized" in the local understanding of the word. Most importantly, they were not Christian.
Vikings' exact reason for venturing out from their homeland is uncertain; some have suggested it was due to overpopulation of their homeland, but the earliest Vikings were looking for riches, not land. In the eighth century A.D., Europe was growing richer, fueling the growth of trading centers such as Dorestad and Quentovic on the continent and Hamwic (now Southampton), London, Ipswich, and york in England. Scandinavian furs were highly prized in the new trading markets; from their trade with the Europeans, Scandinavians learned about new sailing technology and the growing wealth and accompanying inner conflicts between European kingdoms. The Viking predecessor-pirate who preyed on merchant ships in the Baltic sea-would use this knowledge to expand their fortune-seeking activities into the North Sea and beyond.
*Early Viking Raids:-
In A.D.793, an attack on the Lindisfarne monastery off the Northumberland England market began the Viking Age. The culprits-probably Norwegian who sailed directly across the North sea-did did not wholly destroy the sanctuary, but the attack shook the European religious world to its core. Unlike other groups, these strange new invaders had no respect for religious institutions such as the monasteries, which were left unguarded and vulnerable near the shore. Two years later, Viking raids struck the undefended island monastery of Skye and Iona( in the Hebrides) and Rathlin ( off the northeast coast of Ireland). The first recorded raid in continental Europe came in 799, at the island monastery of St Philibert's on Norirmoutier, near the Loire River's estuary.
For several decades, the Vikings confined themselves to hit-and-run raids against coastal targets in the British Isles(particularly Ireland) and Europe(the trading center of Dorestad, 80 kilometers from the North Sea, because a frequent target after 830). They then took advantage of internal conflicts in Europe to extend their activity further inland: after the death of Louis the pious, emperor of Frankia(modern-day France and Germany), in 840, his son Lothar invited the support of a Viking fleet in a power struggle with brothers. Before long other Vikings realized that Frankish rulers were willing to pay them rich sums to prevent them from attacking their subjects, making Frankia Viking activity.
* Conquests in the British isles:-
By the mid-ninth century, Ireland, Scotland, and England had become primary targets for Viking settlement and raids. Vikings gained control of the Northern isles of mainland Scotland. They founded Ireland's first trading towns: Dublin, Waterford, Wexford, Wicklow, and Limerick, and used their base on the Irish coast to launch attacks within Ireland and across the Irish sea to England when kings Charles the Bals began defending West Frankia more energetically in 862, fortifying towns, abbeys, rivers, and coastal areas, Viking forces began to concentrate more on England than Frankia