Marriage is a lifelong partnership of the whole of life, of mutual and exclusive fidelity, established by mutual consent between a man and a woman, and ordered towards the good of the spouses and the procreation of offspring. As the Second Vatican Council reminds us, marriage is not a purely human institution: ―the intimate partnership of life and the love which constitutes the married state has been established by the creator and endowed by him with its own proper laws. . . . For God himself is the author of marriage. Moreover, God has endowed marriage with certain essential attributes, without which marriage cannot exist as he intends.
The Church has taught through the ages that marriage is an exclusive relationship between one man and one woman. This union, once validly entered and consummated, gives rise to a bond that cannot be dissolved by the will of the spouses. Marriage thus created is a faithful, privileged sphere of intimacy between the spouses that lasts until death.
Marriage is not merely a private institution, however. It is the foundation for the family, where children learn the values and virtues that will make good Christians as well as good citizens. The importance of marriage for children and for the upbringing of the next generation highlights the importance of marriage for all society.
Conjugal love, the love proper to marriage, is present in the commitment to the complete and total gift of self between husband and wife. Conjugal love establishes a unique communion of persons through the relationship of mutual self-giving and receiving between husband and wife, a relationship by which a man leaves his father and mother and clings to his wife, and the two of them become one body [flesh] (Gn 2:24).
Click to read the entire "Pastoral Letter of the United States Conference of Catholic Bishops": http://www.usccb.org/issues-and-action/marriage-and-family/marriage/love-and-life/