Nora and Torvald have, what appears on the surface, to be a good marriage according to the standards of the time. This marriage is based on quite distinct and unequal gender roles in which Torvald appears the classic male "breadwinner" and holds the power in the relationship while Nora is a housewife and consumer, treated by Torvald as though she is an innocent child.
The reality of the relationship, as we discover as we progress through the play, is quite different. Nora, in fact, has provided the money to help Torvald take care of a serious illness and by clever housekeeping and part-time work is striving to repay a moneylender.
It turns out, though, that Torvald is only in love with an illusion of Nora and Nora herself has never really seen Torvald as he is, but rather imagines him a sort of romantic hero rather than a practical, somewhat self-centered, and unromantic businessman. As their true characters are revealed at a moment of high stress and conflict, the weakness of their marriage is revealed, and Nora leaves Torvald.
Nora and Torvald do not have an equal partnership in their marriage. Torvald would never consider Nora his equal. He calls her silly little nicknames, scolds her like a child, and views her as his possession.
Torvald feels as if he should have the right to limit her intake of sweets, and chastises her when she cheats. He calls her a spendthrift, and she must beg for money for things.
Nora performs for Torvald at his request, as if she is an entertainer and not a wife. Nora has a secret that is causing her great anguish. Nora does not want to get into "trouble" with Torvald over a forgery that was needed to save his life. She struggles with this secret, and instinctively knows he will not tolerate her transgression.
Once the truth is out, Nora realizes she does not want to be in the type of marriage she is in, and walks away from it, leaving him stunned. Torvald would never have thought her capable of it. He thought she would have to live with whatever type of reaction he chose to have.