Henrik Ibsen illustrates many different characters in his play A Doll's House.
Terms which need to be defined are protagonist, antagonist, round, flat, dynamic, and static.
A protagonist is the main character of the story, or play. An antagonist is the main character who conflicts with the protagonist. A round character is fully described and defined by the author. A flat character is not fully described, the author gives little information about this character. A dynamic character changes (mentally or physically grows) from the beginning of a text to the end. A static character stays the same throughout a text, they do not change.
Nora Helmer is a round character. Given that she is the protagonist of the play, Ibsen fully describes Nora. She also changes throughout the play; this makes Nora a dynamic character.
Torvald Helmer is a round character and Nora's antagonist. Ibsen describes his personality very well (proven by the fact that many readers fail to be engaged by him--he is simply disliked by most). That being said, Torvald is a flat character. He fails to change over the course of the play. This being said, Torvald could be considered a raisonneur (the mouth piece of other characters or the author). This is defined by the fact that he thinks he is in charge of his family, while in reality, he is not.
Nils Krogstad and Kristine Linde are both dynamic and round. Each are described in detail by Ibsen. While the changes are small, each do undergo them.
Dr. Rank, while easily sympathized with, seems to be a rather flat character. The important aspects of his character are given and, while though one's sympathy for him grows, he fails to. Instead, he seems to fade--much like his life given his ailment.
The Helmer children are both flat and static. They do not change and little is really known about them.