Why the title of Partners in the Mission? Let me answer that by quoting the Catechism of the Catholic Church (a best seller):
“Since, like all the faithful, lay Christians are entrusted by God with the apostolate by virtue of their Baptism and Confirmation. They have the right and duty, individually or grouped, to work so that the divine message of salvation may be known and accepted by all throughout the earth. This duty is the more pressing when it is only through them that people can hear the Gospel and know Christ. Their activity in ecclesial communities is so necessary that, for the most part, the apostolate of the pastors cannot be fully effective without it.” (CCC900)
“Lay people also fulfill their prophetic mission by evangelization, that is the proclamation of Christ by word and testimony of life. For lay people this evangelization acquires a specific property and peculiar efficacy because it is accomplished in the ordinary circumstances of the world.” (CCC905).