What does Acts 18:20 mean?

Paul doesn't usually stay very long in any given town, but it seems he is in Ephesus for only a day. He is on his way back to Syrian Antioch after trekking through modern-day Asia Minor, Macedonia, and Athens, before staying in Corinth for eighteen months. When he reaches Ephesus, he has just enough time for a quick stop at the synagogue to explain that Jesus of Nazareth is the Jewish Messiah.

After Paul visits Jerusalem and goes home to Syrian Antioch (Acts 18:22), he will return to Ephesus and stay for three years (Acts 20:31). Though many of the Jews do reject his message and drive him from the synagogue, they don't harass him after he leaves. Instead, Paul is threatened by the silversmiths. The Gentiles so thirst for Jesus' offer of forgiveness and reconciliation with God that they abandon their worship of Artemis and burn valuable magic books. In response, the silversmiths, who make a living selling idols, start a riot and threaten Gaius and Aristarchus, Paul's companions (Acts 19).

For now, Paul will board a ship and continue his voyage home. Ephesus is near the west coast of Asia, the western-most province in Asia Minor. Paul leaves Priscilla and Aquila there and sails to Caesarea Maritima on the Judaean coast. From there, he visits the church in Jerusalem, possibly so he can complete a vow (Acts 18:18), but perhaps for Passover. After an extended stay in Syrian Antioch, Paul will go north again for his third missionary trip (Acts 18:22–23).