What does Acts 18:27 mean?
All things considered, the Jesus-followers in Ephesus work quickly. On his way home from his second missionary journey, it appears Paul spent only one day in the synagogue, explaining how Jesus of Nazareth fits the prophecies of the Jewish Messiah. He leaves behind Priscilla and Aquila and continues on his way (Acts 18:19–21). While worshiping in the synagogue, Priscilla and Aquila hear Apollos preach. A Jew from the academic city of Alexandria, Apollos, knows John the Baptist's message of repentance and some about Jesus, but he doesn't seem to fully understand how Jesus offers reconciliation with God. Priscilla and Aquila pull him aside and show him (Acts 18:24–26).Now, Apollos is ready to move on and spread the story of Jesus. He decides he needs to go to Corinth to continue the work Paul, Priscilla, and Aquila started. The church in Corinth welcomes him, some even trying to turn him into a sect leader (1 Corinthians 1:12). Paul considers him a fellow worker (1 Corinthians 3:9). Apollos builds up those who came to Christ during Paul's eighteen-month stay and continues to try to convince the Jews in the synagogue that Jesus is the Messiah (Acts 18:11, 28).
Achaia is the province that includes the large island-like mass connected to southern Greece by a narrow isthmus. Corinth is the capital of Achaia. The "brothers" are those Jews and Gentile God-fearers who accepted Jesus as their Savior either when Paul was there or through the teaching of Priscilla and Aquila.