Did Jesus work miracles, or are they just pious tales?
Jesus really worked miracles, and so did the apostles. The New Testament authors refer to real incidents.

Even the oldest sources tell of numerous miracles, even the raising of the dead, as a confirmation of Jesus’ preaching: “But if it is by the Spirit of God that I cast out demons, then the kingdom of God has come upon you” (Mt 12:28). The miracles took place in public; some of the persons involved were known by name, for instance, blind Bartimaeus (Mk 10:46-52) or Peter’s mother-in-law (Mt 8:14-15). There were also miracles that in those Jewish circles were considered shocking and outrageous (for example, the cure of a crippled man on the Sabbath, the cure of lepers). Nevertheless they were not disputed by contemporary Judaism.

But why did Jesus work miracles?
The miracles that Jesus worked were signs that the kingdom of God was beginning. They expressed his love for mankind and reaffirmed his mission.

Jesus’ miracles were not self-aggrandizing displays of magic. He was filled with the power of God’s healing love. Through his miracles he showed that he is the Messiah and that the kingdom of God begins in him. Thus it became possible to experience the dawn of the new world: he freed people from hunger (Jn 6:5-15), injustice (Lk 19:8), sickness, and death (Mt 11:5). By driving out demons, he began his victorious advance against the “ruler of this world” (meaning Satan; see Jn 12:31). Nevertheless, Jesus did not remove all misfortune and evil from the world. He directed his attention principally to freeing man from the slavery of sin. His central concern was faith, which he also elicited through miracles.

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 in remembrance of me” (Lk 22:19b).

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.