Definitions for "Apostolate"
The dignity, office, or mission, of an apostle; apostleship.
The dignity or office of the pope, as the holder of the apostolic see.
Christian ministry. The word is derived from the apostles of Jesus Christ sent on mission in his name to preach, heal, and cast out evil spirits. Apostolate can be as varied as the needs of the Church: administration of the Sacraments, preaching, retreats, hospital, military, or prison chaplaincy, counseling, working with youth, married couples or the elderly, etc. Only some apostolates (i.e., administration of the Sacraments) need to be carried out by the clergy. Others can be carried out by any Catholic who desires to serve those in need. For these apostolates to be carried out officially, some form of Church approval or commissioning is necessary. Since Vatican II (1962-65) and its emphasis on the "Apostolate of the Laity," as well as the current shortage of clergy*, more and more Catholic laity* have been involved in some form of apostolate.
Keywords:  entrusted, fulfill, task, sent, someone
a "sent one" someone who is entrusted to fulfill a task while acting in the name of someone else