Though not as well-known as Paul, Barnabas played a large role in the establishment of new churches in the Greek and Hebrew world of his day. Barnabas was the man who took Paul under his wings when no one else wanted to trust Paul. This was because Paul was most known as the great persecutor of the Christian church when Barnabas met him.
Barnabas trained Paul in the ministry and accompanied him on his early missionary travels. Later the two men split up and formed two new teams of church planters. Paul took Silas with him and Barnabas took John Mark.
After Paul and Barnabas separated, the Bible does not say much more about Barnabas. However, Paul acknowledged later in his life that Barnabas had done a good job in training John Mark for the ministry.