There are two main branches, Insular (West-) Scandinavian and Continental (East-) Scandinavian. The former is the "older" (i.e. more conservative) version, talked by Vikings speaking Old Norse to Iceland (Icelandic), Greenland, the Faroes (Faeroese), and the Shetlands and Orkneys. The latter, Continental Scandinavian, is more influenced by neighbouring languages, most notably Low German.
Many dialects in Norway retain the West-Scandinavian features, and Nynorsk, one of the two official written languages of the country, was based primarily on such dialects. Additionally, the dialect of Jämtland in Sweden is classified as West-Scandinavian.
In contrast, new features developed in Danish, Danish-influenced areas of Norway (due to the long Danish rule), and in Sweden (with Finland) to form the Continental varieties. In particular Bokmål, the first written standard language in Norway, and now the dominating official language, is considered Continental.
As a result, Danish and Norwegian may in reality be somewhat more similar to each other than either is to Swedish. Due to the long political union between Norway and Denmark, the Norwegian Bokmål shares much of the Danish vocabulary. In addition, due to Danish pronunciation, Swedes usually find it easier to understand Norwegian than Danish. But even if a Swede finds it difficult to understand a Dane, it is not necessarily the other way around. One witticism about Norwegian that expresses the basic similarities and differences between the languages is that "Norwegian is Danish spoken in Swedish." The relationships between the three languages might be summarized by the following diagram:
+ phonology Norwegian ----------------- Swedish | - vocabulary | - phonology + vocabulary | | DanishThe North Germanic languages are often cited as proof of Max Weinreich's aphorism "A language is a dialect with an army and a navy." The differences in dialects within the countries of Norway, Sweden, and Denmark are often greater than the differences across the borders, but the political independence of these countries leads continental Scandinavian to be classified into Norwegian, Swedish, and Danish in the popular mind. The creation of Nynorsk out of Insular dialects after Norway became independent of Denmark in 1814 was an attempt to make the linguistic divisions match the political ones.
All North Germanic languages are thought to be descended from Old Norse.
Note that divisions between subfamilies of North Germanic are rarely precisely defined; most form continuous clines, with adjacent dialects being mutually intelligible and the most separated ones not.