Catechism of the Catholic Church §2360 — excerpt
Sexuality is ordered to the conjugal love of man and woman. In marriage the physical intimacy of the spouses becomes a sign and pledge of spiritual communion.
This translation is under copyright, so only the cited words are quoted here. Follow the link for the full text. Translation: English translation of the Catechism of the Catholic Church, 2nd ed. (Libreria Editrice Vaticana), as posted at vatican.va.