In Christian tradition, the apostles (Greek: ἀπόστολος, transl.: apostolos; lit. "one who is sent on a mission"), sometimes referred to as the Twelve Apostles, were a small group of twelve people reported to be the disciples of Jesus, the central figure of Christianity.[1] They are Jewish messengers sent by Jesus to preach the gospel, initially only to Jews and then also to Gentiles, throughout the ancient world. During Jesus' life and ministry in the 1st century, the apostles were his closest followers and became the main preachers of his gospel message.
Apostle means "sent". The apostles were 12 people who accompanied Jesus and had intimacy with Him. Jesus gave special training to the apostles, to proclaim the gospel and to found His Church.
The 12 apostles were Simon (Peter), Andrew, James (son of Zebedee), John, Philip, Bartholomew, Thomas, Matthew, James (son of Alphaeus), Thaddeus (Judas), Simon (the Zealot), and Judas Iscariot (Matthew 10:2-4; Luke 6:13-16).
They accompanied Jesus during His ministry and were called to proclaim the gospel to the world. After Pentecost, they became the leaders of the early church, teaching what they had learned from Jesus and creating a solid foundation for the growth of the church.
They traveled to other lands and founded churches in many places through their testimonies about Jesus and miracles. Much of the information in the Gospels was probably provided by the apostles.

The Twelve Apostles of Christ: Study on the life of the Apostles