As far as I understand, the viking peoples were marked by their coastal raiding of other regions across Europe. While this era is commonly said to have ended in or around 1066, I was reading a book on Polish history that mentioned Denmark and the "Scandinavian kingdoms" advancing into eastern Europe (Lithuania and Latvia are used as examples) in the mid to late thirteenth century, assumedly to take territory.
I know I'm not giving many details to go on, but what would be the difference between these incursions and those carried out by the vikings? To specify a bit further, why are these groups not considered to be vikings although their purpose appears to be similar?
It may be Christianity. 'Vikings' (a generic term that refers to a whole bunch of people) is a term that is often applied to marauders, pagans from the Scandinavian lands who loot and descrate Christian sites (because they have all the shiny stuff). While England was Christian long before 1066, there were still descendants of the Danes who had settled in England. Harold Godwinson was defeated by William the Conqueror, but before the battle of Hastings that saw William proclaimed king, Harold had to fight another battle, Stamford Bridge, which he won; this was a against the Norwegian king, Harold Hardrada, who was killed there. Harold Hardrada was an uncommited (although very interested) Christian, so this element of paganism may have died with him. The point being, that the kingdoms of Scandinavia became fully christian entities, reconised by the Church in Rome and thus having to sort of respect another Christian king, and thus to sort of justify invading their territory. William was also a very dominant character, having extensive territory in France as well as England. So these areas would have been seen as too much effort to attack.
However, the biggest thing is this: that links between Scandinavia and the Eastern Europe pre-dated 1066 - trade routes with the Arab world are known from before this time, and utilised river systems to travel across Europe. they also had strong links to Byxantium, and served as mercenaries for the empire. During this time 'vikings' also fought as mercenaries for various factions in the the area referred to as Kievan Rus, so were heavily involved in politics and intermarried (Harold Hardrada married politically to a lady called Elisiv from Kiev).
Simply put, their purpose was not really similar; to the west they looted and robbed. this eventaully lead to settlements and integration. This immigration was halted by 1066, and William's rule made England an unwelcome place (he made it pretty rough on the native Anglo-Saxons as well). So any push out for territory would have been forced in the opposite direction - east, where they already had a history political alliances, trade and emigration. By this time, the looting and robbing was not the objective, hence the change in loss of the perjorative term 'viking'.