When people divorce, they need to divide their assets and determine liability for their debts. All "marital" property -- the assets and debts that the parties accumulated during their marriage -- is subject to such a division. Nonmarital property is anything given as a gift or inheritance to only one of the spouses, or acquired before or after the marriage.
If there is no agreement on how to divide assets and debts, the court will make an "equitable" division. This does NOT necessarily mean an equal division. For example, if one person has greater income, it may be equitable to assign that person a greater portion of the marital debt.