God created man and woman out of love and commanded them to imitate His love in their relations with each other.
Man and woman were created for
each other. “It is not good for the man to be alone. I will make a suitable partner for him… The two of them become one body” (Gn 2:18; 24). Woman and man are equal in human dignity, and in marriage both are united in an unbreakable bond.

The Sacrament of Marriage is a covenant, which is more than a contract. Covenant always expresses a relationship between persons. The marriage covenant refers to the relationship between the husband and wife, a permanent union of persons capable of knowing and loving each other and God.

The celebration of Marriage is also a liturgical act, appropriately held in public liturgy at church. Catholics are urged to celebrate their marriage within the Eucharistic Liturgy.

The marriage covenant, by which a man and woman form with each other an intimate communion of life and love, has been founded and endowed with its own special laws by the Creator. By its very nature it is ordered to the good of the couple, as well as to the generation and education of children. Christ the Lord raised marriage between the baptized to the dignity of a sacrament. –CCC, no. 1660

Married love is ordered to the good of the spouses and to the procreation and education of children. These are the unitive and procreative purposes of marriage. The fruitfulness of married love includes the moral, spiritual, and faith life the parents hand on to their children. Parents, as principal educators of their children, are at the service of life.
Not all married couples are able to have children. “Spouses to whom God has not granted children can nevertheless have a conjugal life full of meaning… [and] can radiate a fruitfulness of charity, of hospitality and of sacrifice” (CCC, no. 1654).

The first effect of the Sacrament of Matrimony is the gift of the bond between the spouses, "The consent by which the spouses mutually give and receive one another is sealed by God Himself” (CCC, no. 1639).

The grace of this Sacrament perfects the love of husband and wife, binds them together in fidelity, and helps them welcome and care for children. Christ is the source of this grace and He dwells with the spouses to strengthen their covenant promises, to bear each other’s burdens with forgiveness and kindness, and to experience ahead of time the “wedding feast of the Lamb” (Rev 19:9).

The promise to remain exclusively faithful until death, made before God in the midst of family and friends before an authorized priest or deacon, is supported by the continuing presence of Christ in the life of the spouses as he pours into their hearts the gift of love through the Holy Spirit. The couple does not walk alone and possesses the graced freedom to respond to all natural and supernatural help.

Together the couple must seek the same goals of mutual love united to Christ’s love, the raising of a family and the continued growth of their own relationship.

It can seem difficult, or even impossible, to bind oneself for life to another human being. This makes it all the more important to proclaim the Good News that God loves us with a definitive and irrevocable love, that married couple share in this love, that it supports and sustains them, and that by their own faithfulness they can be witnesses to God’s faithful love. Spouses who with God’s grace give this witness, often in very difficult conditions, deserve the gratitude and support of the ecclesial community. (CCC, no. 1648)

  -taken from the United States Catholic Catechism for Adults