JP II beautifully explains the institution of marriage and what it symbolizes – something our modern society is trying its best to dismantle on a daily basis:
They key for understanding marriage remains the reality of the sign with which marriage is constituted on the basis of man’s covenant with God in Christ and the Church: is is constituted in the supernatural order of the sacred bond requiring grace. In this order, marriage is a visible and efficacious sign. Having originated in the mystery of creation, it draws its new origin from the mystery of redemption in order to serve the “union of the sons of God in truth and love” (Gaudium et Spes, 24:3). The liturgy of the sacrament of Marriage gives a form to that sign: directly, during the sacramental rite on the basis of the ensemble of its eloquent expressions; indirectly, throughout the whole of life. As spouses, the man and the woman bear this sign throughout the whole of their lives, and they remain this sign until death.
— John Paul II, General Audience of Jan. 5, 1983 TOB 103:7
Related: TOB Tuesday: The Call to Marriage