Dialects and Slang

I found myself talking to natives of an area south of Trondheim and they confirmed that the name Skutese means "fleet" or "many ships" but that is a local slang, particular of that area. They told me that in Norway there are lots of dialects and slang variations that, sometimes, people from the south can't understand the language from the north unless it's Nynorsk, Bokmal or English. Is it true? Because if so the search narrows to one particular area. Thank You Aurora