What is an Apostle?
Apostle is a term applied chiefly to the original disciples of Jesus who became the leading missionaries and heads of the Christian church after the Resurrection. The word comes from the Greek apostellein (to send away) and literally means "one sent," as on a mission. The names of the original Twelve Apostles are given in the New Testament (Mark 3:14-19, Matthew 10:1-4, Luke 6:12-16, and Acts 1:13) as follows: Simon (called Peter), James (or Jacob), John (James' brother), Andrew (Peter's brother), Philip, Bartholomew, Matthew, Thomas, James (or Jacob, the son of Alphaeus), Thaddaeus (called Lebbaeus in some manuscripts), Simon "the Cananaean," and Judas "Iscariot," who betrayed the master. Judas' place was later taken by Matthias (Acts 1:15-26). In Mark 2:14, "Levi the son of Alphaeus" was called to be a disciple; in Matthew 9:9, he is said to have been called Matthew, though Luke 5:27 retains the name Levi. In Luke 6:15, Simon the Cananaean is called "the Zealot," and in the following verse Judas, the son (or brother) of James, is mentioned.
Jesus began His ministry in Galilee by proclaiming His message about God to the great crowds that nocked to hear Him; but He was soon faced by two dangers that made Him change His plan of campaign. One was that His enemies (the Jewish religious authorities) were plotting against His life ; He realized that at any moment He might be arrested and killed and that He must therefore make sure that His work would be carried on after His death. The other danger was that the people were beginning to regard Him as a political leader instead of a religious one and wanted to make Him their "king", hoping that He would lead a revolt against the Romans occupying their country.
Time was short and Jesus could not afford to let this dangerous situation develop any further. So, while He still went on teaching and healing the people, He decided to concentrate on a small group of specially chosen followers, whom He could teach and train and later send out to carry His message.
Jesus must have had scores of such followers ("disciples" as they were called), and out of these, after a whole night spent in thought and prayer, He selected 12. These 12 were called the apostles, from the Greek word apostolos, meaning "one who is sent out", an ambassador or an envoy.
In addition to the original Twelve, other missionaries and leaders, such as Barnabas (Acts 14:14) and Paul, were given the title "apostle". Paul laid great stress upon his apostleship, describing himself as an "apostle to the gentiles" (Romans 11:13) and claiming both to have seen the Lord in a vision (I Corinthians 9:1, 15:8) and to have worked miracles (II Corinthians 12:12). It is probable that the apostles had wives (I Corinthians 9:5), though the later account of Peter's daughter, Petronilla, has no New Testament support. The reference in Romans 16:7 to Andronicus and Junias is often taken to mean that they were apostles, but the sounder interpretation of the phrase "of note among the apostles" is that they were well known to the apostles as leaders in the church.