The film is based on Kaptein Sabeltann, a character created by Terje Formoe which gained popularity in Norway om the early 90s. The character is widely popular among children, with shows, music and merchandising. Based on this premises the movie provides no introduction on who the characters are, as the main target (children in Norway) know him well.
The movie itself is a light history around pirates, with some light jokes, action and everything that a child would like to see.
The main character (Sabeltann) is not always the good or the bad guy and that is part of the culture built around him.
In general it's a decent child's movie if they are aware or the background.
When translated to other languages the songs may be less catchy to the ear and the lack of presentation of the main characters can be confusing to some older viewers seeking to understand the history behind.