What does Acts 6:12 mean?

The "council" is a reference to the Sanhedrin, the religious court of the Jews. They enforced the Mosaic law on Jews in Judea and beyond (Acts 9:1–2). Members of the Sanhedrin were typically either priests, teachers of the Law, or elders: respected businessmen of Jerusalem. They could belong to any sect of Judaism, though most belonged to the Sadducees, who did not believe in the resurrection of the dead. Others were Pharisees, who added extra laws to those God gave Moses. Not everyone on the Sanhedrin rejected Jesus; Joseph of Arimathea and Nicodemus followed Jesus and were on the council (Luke 23:50; John 7:50–51).

This is a near copy of how the Jewish council treated Jesus. The Sanhedrin falsely accused Him of threatening to destroy the temple, a capital offense in the Roman Empire (Mark 14:57–58), and then incited a crowd with lies (Matthew 27:20). In this case, Jews from Africa and modern-day Asia Minor incite a crowd so that the Sanhedrin will condemn Stephen.

The Sanhedrin is more than happy to oblige. They have arrested (Acts 4:3; 5:18), threatened (Acts 4:18), and beaten (Acts 5:40) the leaders of the Jesus-followers to no avail. The members of the Sanhedrin are jealous of the apostles' following and powers (Acts 5:17) and horrified that they not only teach that resurrection of the dead is possible, but also that Jesus of Nazareth, their sworn enemy, has risen (Acts 4:1–2).

Despite this, many of the priests have chosen to follow Jesus (Acts 6:7). There's no telling how this affects the body of priests or the Sanhedrin. The priests are all of one family (Deuteronomy 18:1); Jesus' warning that He would split families is coming true (Luke 12:49–53).