23 Although every disciple of Christ, as far in him lies, has the duty of spreading the Faith, Christ the Lord always calls whomever He will from among the number of His disciples, to be with Him and to be sent by Him to preach to the nations (cf. Mark 3:13). Therefore, by the Holy Spirit, who distributes the charismata as He wills for the common good (1 Cor. 12:11), He inspires the missionary vocation in the hearts of individuals, and at the same time He raises up in the Church certain institutes which take as their own special task the duty of preaching the Gospel, a duty belonging to the whole Church. They are assigned with a special vocation who, being endowed with a suitable natural temperament, and being fit as regards talent and other qualities, have been trained to undertake mission work; or be they autochthonous or be they foreigners: priests, Religious, or laymen. Sent by legitimate authority, they go out in faith and obedience to those who are far from Christ. They are set apart for the work for which they have been taken up (cf. Acts 13:2), as ministers of the Gospel, "that the offering up of the Gentiles may become acceptable, being sanctified by the Holy Spirit" (Rom. 15:16).
Source: Ad Gentes (Vatican.va)