Christ’s instruction to the apostles was a great call to those who became the first bishops and the first missionaries of the Church. They were told to go ad gentes—that is, “to the nations,” to those who did not know Christ—and to proclaim the Gospel. Because the apostles were faithful and obedient to Christ’s command, his Church has grown and flourished.

Missions are those “particular undertakings by which the heralds of the Gospel, sent out by the Church and going forth into the whole world, carry out the task of preaching the Gospel and planting the Church among peoples or groups who do not yet believe in Christ. . . . The proper purpose of this missionary activity is evangelization” (Ad Gentes, no. 6).