Marriage is a private bond between two people, but it is also an important social institution. Most states define marriage as a civil contract between a man and a woman to become husband and wife.

The moment a man and a woman marry, their relationship acquires a legal status. Married couples have financial and personal duties to each other during marriage and after separation or divorce. State laws determine the extent of these duties. As the U.S. Supreme Court said about marriage in 1888: "The relation once formed, the law steps in and holds the parties to various obligations and liabilities."

Society recognizes marriage in several ways:

• As a way to express commitment, strengthen intimate bonds, and provide mutual emotional support.
• As a (comparatively) stable structure within which to raise children.
• As a financial partnership in which spouses may choose from a variety of roles. Both spouses may work inside or outside the home to support the family, or the husband may support the wife, or the wife may support the husband.

As our society becomes more complex, there is no longer a short answer to the question "What is marriage?" Definitions and opinions of the proper functions of marriage continue to change. The women's rights movement and gay rights movement have resulted in more equal treatment of men and women and the creation of new legal relationships, including domestic partnerships and civil unions for same-sex couples. The traditional concept of marriage remains, but it continues to evolve.