Jesus' 12 apostles, according to the books of Matthew and Luke in the Bible, were Peter, Andrew, James the son of Zebedee, John, Philip, Bartholomew, Thomas, Matthew, James the son of Alphaeus, Thaddaeus, Simon and Judas Iscariot. The twelve were among Jesus' closest followers, and spread Christianity after his death.
Some of the 12 apostles' names changed after they started following Jesus. For example, Peter's name was originally Simon, but Jesus changed his name to Peter to signify the foundational place the former fisherman would play in the Christian community. In addition, the Bible gives descriptions to some of the apostles, which can vary among the Gospels. For example, Matthew 10 identifies Matthew as a tax collector; Matthew 10 also refers to Simon as "the Cananaean," while Luke 6 calls him "the Zealot."
Some of the apostles played a crucial role in the life and ministry of Jesus. For example, Judas Iscariot later became a traitor, and betrayed his former master to the authorities. The Bible records that Judas later hanged himself for this act, and that the apostles chose Matthias (or Thaddeus) as Judas Iscariot's replacement.
Although he is often called an apostle, St. Paul was not a member of the original 12 apostles.