Everything the husband and wife own separately. In a community property state, this includes property received as a gift or an inheritance, obtained before the marriage, and property purchased with those assets.
In common law separate property states (i.e., every state except Arizona, California, Idaho, Louisiana, Nevada, New Mexico, Texas, Washington, and Wisconsin), the person whose name is on the title document (e.g., a deed, an account registration, etc.) is the property owner. If there is no title document, the person who paid for the property owns it. Money earned by one spouse remains his or her separate property. If both spouses put their names on a title document, they own the property jointly.
If a couple in a separate property state divorces, a court will distribute the spouses' property in a fair way. In some cases, this may result in a property division similar to what would occur in a community property state.