Apostle- Representative of God to earth. Often referred to as "bond servant" of Christ. A bond servant was a slave of over seven years, who determined to obey his master for life, rather than going free.
Jesus chose 12 Apostles amongst his desciples:
The First Pope
Simon (Who denied Jesus Three Times, but later accepted him Three times, and is given his sheep to take care of (- Simon means Read -Later Names Peter, meaning Rock, when Jesus said - "I say to you- you are Rock and on this Rock, I built my church" - he became Simon, or Simon Peter - note the Gospel of Mattew was originally written in Hebrew, where the Name Peter, and the Word Rock are likewise).
Boanerges ("Sons of Thunder")
James - the Son of Zebedee
John- the Brother of James
Thomas (Who doubted the Resurrection, but was forgiven)
James - son of Alphaeus
Simon - The Zealot
Judas Iscariot, the man who was a traitor to Jesus.
Matthias- After the betrayal, Judas Suicide, and Jesus Resurrection- Matthias was chosen to replace Judas, via a Lot. (A lot was a chance device, that was used here to choose between Matthias and Joseph, known as Barsabbas.