Vikings are generally seen as a group of people from Scandinavia/Nordic countries (i.e Denmark, Sweden, Iceland, Norway, Islands like Gotland and other coastal towns around the Baltic sea). But they must've consisted of groups in these countries, i.e Geats/Götar, Danes, Jutes/Jutar, Svear or whatever they might be.
If you see the word 'viking' as the occupation it is, what groups of people did it actually consist of, was there cultural differences between these groups and so forth?
A great article just came out in November addressing this very issue:
Most of the textual accounts suggest that viking bands were raised by chieftains recruiting from their home fjord. Archaeological evidence contradicts this. So far, we've been able to do the necessary isotopic analysis of four viking cemeteries—9th-century Dublin (n=4), 9c Repton, England (n=3), 10c Ridgeway, England (n=38), and 10c Trelleborg, Denmark (n=52). Although this is only a small statistical smattering from the Viking Age, the results are unanimous: whether at home or abroad, viking warbands had diverse origins. Of the 52 individuals buried at Ridgeway, at least 38 came from points outside the UK, including Iceland, the Baltic states, and Belarus. It's hard to imagine what these diverse groups would have spoken, and one recent study suggests that each group developed its own unique pidgin version of Old Norse as a lingua franca. War leaders counteracted this heterogeneity by actively building group cohesion. The authors in the article above point to material markers (e.g. carrying similar weapons), oath-taking, and shared ideology (e.g. adopting a Norse paganism).
With regard to the specific groups you mentioned, they actually describe not only different groups but different types of groups. Geats/Götar are an old term that was revived throughout the early middle ages to describe different peoples at different times—there's no reason to equate the semi-mythical Geats in Beowulf to the later Gotlanders, for example. Danes likewise had different meanings depending on who was using it. Western Europeans typically referred to anyone who spoke Old Norse as Danish, although there were also early kingdoms forming in the area of modern Denmark that were called Danish. The Jutes were in some ways an invention of Anglo-Saxon historians who were trying to claim a Germanic ancestry. There's no material evidence for a distinct "Jutish" community and certainly no textual evidence attesting to a Jutish identity until the middle ages were well under way. Finally, the Svear are the least ambiguous, describing a kingdom centered around the area north of modern Stockholm, although our sources on the Svear for much of the Viking Age are often legendary or otherwise historically unreliable. So these words variously represent ethnic groups, geographic regions, and political affiliations, but they rarely if ever mean all three things at once (compare to our modern concept of nation-state). For a more complete discussion of the names of various groupings in Scandinavia, see the excellent article:
The word "viking" is said to come from the old Norse word "vikingr", which would mean "raid" or "to pirate". There is also another hypothesis which I heard in a radio program about the vikings made in the early 2000s, which says that it could have also meant "men of the vik", with vik being either a trading center or the fjords of southern Norway.
Generally viking raiders, traders and explorers to the west, i.e England, Frankia, Hispania and further were from Norway, Denmark and Frisia i.e modern day Netherlands, while the viking raiders, traders and explorers to the east consisted mostly of Svear i.e Swedes, but they also hired coastal Finns as help, like to guide them on the southern coast of Finland.
However, after norsemen stopped their viking raids in the 11th century, "viking" activity in the Baltic sea did not cease, as the peoples living in the southern coast of the Baltic sea, e.g Prussians, Livonians etc. started doing the majority of raiding, but as the Northern Crusades kicked off and started converting the South- and East Baltic, even these lands became Christians and no more major pagan raids happened in the Baltic. Of course, piracy was a thing even in the middle ages, but that's going to a tangent.
Sadly, I do not really know much of the cultural differences between Norsemen and Frisians, except that they spoke different languages (the Norsemen spoke dialects of Old Norse and the Frisians spoke Old Frisian) and that Christians were more common in Frisia than in Norway, Denmark or Sweden. The Baltic peoples were not of Germanic stock like Norsemen and Frisians, and their languages were completely different and so was their religion.