Thanks for your question. Thomas was one of the
twelve Apostles chosen by Jesus as recorded in Matthew 10:1-4. The word Didymus means
"A twin", so Thomas was one of twins born to his mother. As to his reason for
being absent from the meeting it seems to be because he had lost his faith. He thought
Jesus had died and to continue meeting was hopeless. Even though Jesus had often spoken of
His resurrection from the dead, the message had never really been understood by the
twelve. So Thomas doubted the usefulness of meeting. He was doubting that what he had been
doing for the last three and a half years was useful. But when he came the next week and
Jesus appeared to him as recording in John 20:24-29 brought his faith back and he
continued until death as a faithful servant of Christ.
It should be encouraging to us when we have doubts
that even one of the apostles struggled with the same thing but overcame.