The differences between the Norwegian dialects primarily arose due to history. Norwegian Bokmal is known as the "book language" and more closely resembles that of Danish. Norwegian Nynorsk is known as "New Norwegian" and tends to be closer to the historic spoken Norwegian language that survived under Danish rule in villages and more rural areas. Today Norwegian Bokmal is the most common written form of the language, but people speak numerous dialects and most of these dialects more closely resemble Norwegian Nynorsk. No matter the dialect, all are mutually intelligible.
The Sami language falls into the Uralic family of languages, which includes Hungarian, Finnish, and numerous smaller languages from Central Asia. The ethnic Sami speak this language, but few ethnic Norwegians learn it. Other than the Sami learning Norwegian and some people also learning Swedish or Norwegian, English is overwhelmingly the most popular second language in Norway.
Religion
Most of Norway's population nominally belongs to the Church of Norway, which is an evangelical Lutheran church. There are also various other religions practiced, but in much smaller numbers. The Church of Norway was established in 1536 after the reformation, which was led by Denmark, who controlled Norway at the time. Since this time the state and the church have been closely intertwined as the church fell under the direct jurisdiction of the king (with the exception of World War II when the church refused to work with the Nazi-appointed government). Not surprisingly this religion is almost identical to the state religion of Denmark.
Prior to this time the people were Catholic, which they primarily converted to in the 900s and 1000s under the rule of King Olaf II (later St. Olaf), who is buried in Nidaros Cathedral in Trondheim. They remained Catholic from this time until the 1530s when the Danes forced Protestantism on them. The Norwegians were slow to accept this conversion, but later fully embraced it and when they gained nominal independence in 1814 they recognized the Church of Norway as the state church and religion. Despite the close ties between the church, the people, and the government, few Norwegians are overly religious today and very few people practice regularly.