A NATURAL INSTITUTION
Marriage is a practice common to all cultures in all ages. It is, therefore, a natural institution, something common to all mankind. At its most basic level, marriage is a union between a man and a woman for the purposed of procreation and mutual support, or love. Each spouse in a marriage gives up some rights over his or her life in exchange for rights over the life of the other spouse.
While divorce has existed throughout history, it has been rare until recent centuries, which indicates that, even in its natural form, marriage is meant to be a lifelong union.
The Elements of a Natural Marriage
As Father John Hardon explains in his Pocket Catholic Dictionary, there are four elements common to natural marriage throughout history:
It is a union of opposite sexes.
It is a lifelong union, ending only with the death of one spouse.
It excludes a union with any other person so long as the marriage exists.
Its lifelong nature and exclusiveness are guaranteed by contract.
So, even at a natural level, divorce, adultery, and "homosexual marriage" are not compatible with marriage, and a lack of commitment means that no marriage has taken place.
A SUPERNATURAL INSTITUTION
In the Catholic Church, however, marriage is more than a natural institution; it was elevated by Christ Himself, in His participation in the wedding at Cana (John 2:1-11), to be one of the Seven Sacraments. A marriage between two Christians, therefore, has a supernatural element as well as a natural one. While few Christians outside of the Catholic and Orthodox Churches regard marriage as a Sacrament, the Catholic Church insists that marriage between any two Baptized Christians, as long as it is entered into with the intention to contract a true marriage, is a Sacrament.
THE MARK AND EFFECT OF THE SACRAMENT
The spouses are the ministers of the Sacrament of Marriage because the mark—the external sign—of the sacrament is not the wedding Mass or anything the priest might do but the marriage contract itself. This does not mean the wedding license that the couple receives from the state, but the vows that each spouse makes to the other. As long as each spouse intends to contract a true marriage, the Sacrament is performed.
The effect of the Sacrament is an increase in Sanctifying Grace for the spouses, a participation in the divine life of God Himself.
THE UNION OF CHRIST AND HIS CHURCH
This Sanctifying Grace helps each spouse to help the other advance in holiness, and it helps them together to cooperate in God's plan of redemption by raising up children in the Faith.
In this way, Sacramental Marriage is more than a union of a man and a woman; it is, in fact, a type and symbol of the divine union between Christ, the Bridegroom, and His Church, the Bride. As married Christians, open to the creation of new life and committed to our mutual salvation, we participate not only in God's creative act but in the redemptive act of Christ.
Taken from About Religion Website: