What does Acts 18:23 mean?

Paul is starting his third missionary journey. As in Acts 15:41—16:5, Luke skips over the places Paul has already visited, preferring to focus on new territory. At different times, Paul's companions include Timothy and Erastus (Acts 19:22), Gaius and Aristarchus (Acts 19:29), Luke, and others (Acts 20:4–5).

"There" is Syrian Antioch. About twenty miles from the northeast coast of the Mediterranean Sea, it was the third largest city in the Roman Empire, after Rome and Alexandria, and an endpoint of the Silk Road. Jesus-followers from Cyrene and Cyprus first took the story of Jesus to Antioch while fleeing Paul's persecution before his conversion. The leadership in Jerusalem heard about the growing church and sent Barnabas to validate their beliefs. He found such enthusiasm for the gospel that he went to Paul in nearby Tarsus and invited him to help teach. Jesus-followers were first called "Christians" in Antioch, and it had been Paul's headquarters ever since (Acts 11:19–26).

Galatia is the large district in modern-day central Turkey. During Paul's first missions journey, he and Barnabas planted churches in Pisidian Antioch, Iconium, Derbe, and Lystra (Acts 13:13—14:23). On Paul's second trip, he and Silas returned to the area, meeting Timothy in Lystra (Acts 16:1–5).

Phrygia is a smaller region with ever-changing borders between Galatia and Asia, the large district in modern-day western Turkey. It included the cities Colossae, Laodicea, and Hierapolis. When Paul wrote his letter to the Colossians, he hadn't been to any of these cities (Colossians 1:3–4; 2:1; 4:13), but they're on the way to his main objective: Ephesus (Acts 19:1).