What does Acts 13:2 mean?

The leadership of the church in Syrian Antioch is praying and fasting. It's not clear if they are doing so because of a specific need but "while" fasting probably means it's a regular practice. The group includes several prophets and teachers including Barnabas, Simeon, Lucius, Manaen, and Saul (Acts 13:1).

The Bible does not require Christians to fast, and individual fasting was not common in the Old Testament. Still, fasting from food can be a way to discipline the body and symbolically remove oneself from the distractions of the world and focus on God. While the men are fasting and worshipping, they are submitting to the Holy Spirit, willing to do what He commands.

Barnabas has the gift of prophecy; that is, he admonishes and encourages in truth. Saul is a teacher. Later, Saul will write to the church in Corinth that teaching is of a lower rank than prophecy (1 Corinthians 12:28). It isn't until Acts 13:9, when Saul is in the middle of confronting a false Jewish prophet on behalf of a Gentile ruler, that he is called by his Greek name, Paul. And it isn't until after that significant event that his name precedes Barnabas' (Acts 13:13). Even then, Barnabas is still recognized as Saul's superior in the church in Jerusalem (Acts 15:12, 25).

Although the Holy Spirit honors the prayers of the leaders of the church in Antioch by giving specific guidance, we shouldn't assume that God will always tell us exactly what to do. Sometimes He has a specific plan for us, but more often His "plan" is for us to live our lives considering what the Bible teaches. Not all of us are called to fulltime ministry, but we are all called to live for Christ wherever we are.