A quick definition of mariage de convenance:

Marriage is when two people legally agree to be husband and wife. They must both agree to get married and follow the rules set by the law. There are different types of marriages, like a common-law marriage where the couple lives together and acts like they are married, or a confidential marriage where only the couple and the person who marries them know about it. Some marriages are not allowed, like if the couple is too closely related or if one person is already married. If a marriage is not valid from the beginning, it is called a void marriage and can be ended without a divorce.