Icelandic is the official language of Iceland. Other communities of Icelandic-speaking people can be found in Denmark, the USA, and Canada.
Being a conservative language, spoken on a relatively remote island, that used to be quite isolated, Icelandic is not spread very wide outside Iceland.
Aside from a little over 300,000 Icelandic speakers in Iceland, it is spoken by about 8,000 people in Denmark, 5,000 people in the United States, and more than 1,400 people in Canada, notably in the region known as New Iceland in Manitoba which was settled by Icelanders beginning in the 1880s. Unfortunately, no data is available on the number of people learning Icelandic as a second language.
Icelandic is often considered to be one of the hardest languages to learn. While the difficulty of the language is somewhat exaggerated, there are a few peculiarities that can make it hard to learn.
The more challenging aspects include the noun and adjective inflections (3 genders and 4 cases, irregular morphology), and some finer points of Icelandic pronunciation. The complex system of inflections is typical to other Scandinavian languages and can seem daunting but can be mastered if you put in the work.
Icelandic is an ancient Norse Viking language. It's an old Germanic language that Norwegians used to speak in the past. The Norwegian language has developed, changed and was extensively influenced by other languages over the past thousand years. Icelandic has not. In fact, Icelanders are often asked to read old Norse script to translate as the old language is so far away from the current Norwegian language.
The two languages still share quite a lot of similarities, and speakers of Icelandic and Norwegian can understand each other in every-day situations if they speak slowly and clearly.
Icelandic belongs to the North-Germanic languages, which is a subgroup of the Germanic languages.
This subgroup is also often called the Scandinavian languages, in which Icelandic forms the western group together with Faroese and Norwegian (in particular, spoken Norwegian dialects). Based on the geographical classification, Icelandic belongs to the Insular Scandinavian language together with Faroese.