The following is an excerpt from the Catechism of the Catholic Church, Articles 74-83:
74 God “desires all men to be saved and to come to the knowledge of the truth”: that is, of Christ Jesus. Christ must be proclaimed to all nations and individuals, so that this revelation may reach to the ends of the earth:
God graciously arranged that the things he had once revealed for the salvation of all peoples should remain in their entirety, throughout the ages, and be transmitted to all generations.
The Apostolic Tradition
75 “Christ the Lord, in whom the entire Revelation of the most high God is summed up, commanded the apostles to preach the Gospel, which had been promised beforehand by the prophets, and which he fulfilled in his own person and promulgated with his own lips. In preaching the Gospel, they were to communicate the gifts of God to all men. This Gospel was to be the source of all saving truth and moral discipline.”
In the apostolic preaching…
76 in keeping with the Lord’s command, the Gospel was handed on in two ways: