A miracle is a gift or fruit of the Holy Spirit that is perceived by the senses and does not abide by the order of nature. For example, a miracle can disobey the law of the conservation of matter as in the multiplication of loaves in the New Testament. If a circumstance can be replicated within the bounds of nature, it is not a miracle. Although humans can disrupt the order of nature, they cannot break the order of nature. Therefore, any situation in which the order of nature has been broken is a divine act. However, acts of God such as creation and the sacraments are not miracles because they belong to the order of divine providence and are beyond the senses.
Miracles can occur as a result of prayer and petitioning for intercession through use of relics or visits to holy sites. God can perform a miracle directly or by instruments. When God uses an instrument to perform a miracle, that instrument does not have the power to implement the miracle again at will.
.“Miracle.” EWTN, 1996, http://www.ewtn.com/catholicism/library/miracle-10338.
The effect of a miracle can only be to enhance the good of man or it is not a miracle. The purpose of a miracle is to teach, provide evidence to confirm the truth of the divine mission, and verify the sanctity of the saints. Miracles have always occurred throughout all of time. In the Old Testament, God used Moses to perform miracles to display his power and love for His chosen people. In the New Testament, Jesus performed miracles to help Christians to grasp God’s nature and mission more fully and illustrate the power of faith and prayer. When Jesus heals the paralytic, he shows that he has the power to forgive sins. His multiplication of loaves symbolizes the eucharist and raising people from the dead foreshadowed his ressurection and victory over sin and death. Finally, Jesus gave bestowed the ability to perform miracles to his apostles and those who believed in him.
Miracles help bring people to the Catholic Church because the miracle has an effect on not only the recipient of the miracle but those around him and those who come to believe as a result.
“Gift of Miracles.” EWTN, 1996, http://www.ewtn.com/catholicism/library/gift-of-miracles-10339.