From YOUCAT, fact 92:
92: Why did Jesus call apostles?
Jesus had a large circle of disciples around him, both men and women. From this circle he selected twelve men whom he called APOSTLES (Lk 6:12-16). The apostles were specially trained by him and entrusted with various commissions: “He sent them out to preach the kingdom of God and to heal (Lk 9:2).” Jesus took only these twelve apostles with him to the Last Supper, where he gave them the command, “Do this is remembrance of me (Lk 22:19b).” [551-553, 567]
The apostles became witnesses of Jesus’ Resurrection and guarantors of the truth about him. They continued Jesus’ mission after his death. They chose successors for their ministry: the bishops. To this day, the successors of the apostles exercise the authority conferred by Jesus: They govern and teach and celebrate the liturgy. The cohesiveness of the apostles became the foundation for the unity of the CHURCH (APOSTOLIC SUCCESSION). Preeminent once again among the Twelve was Peter, on whom Jesus bestowed special authority: “You are Peter, and on this rock I will build my Church (Mt 16:18).” From Peter’s special role among the apostles developed the papal ministry.