What does Mark 8:27 mean?

After an apparently short stop on the western shore of the Sea of Galilee, Jesus and the disciples travel twenty-seven miles north, back into the tetrarchy of Herod Antipas' half-brother Philip. Caesarea Philippi—literally "Philip's homage to Caesar"—was a city on the base of Mt. Hermon near the headwaters of the Jordan River. Originally called Paneas, it had been the center for the worship of the Greek god Pan. When Philip the Tetrarch took control, he built it up, made it the administrative capital of his region Iturea, and renamed it in honor or Caesar. Unlike Decapolis, it is within the borders of the land God promised to Israel. It stands in contrast to Caesarea Maritima which sat on the Mediterranean coast. Caesarea Maritima is where Cornelius lived (Acts 10) and where Paul was a prisoner of Felix and Festus (Acts 23:23ff).

The text doesn't say that Jesus and the disciples entered into the city itself. Matthew 16:13 says "the district of Caesarea Philippi" and Mark says "the villages of Caesarea Philippi. " The Greek root word for "village" is kome which refers to the area where the laborers slept; we would say a "bedroom community."

Apparently, the conversation occurs when the disciples interrupt Jesus' attempt to pray alone (Luke 9:18). The use of the term "disciples" instead of "the Twelve" suggest that more than the original twelve disciples are present.

"On the way" may just mean that they were walking or in between destinations, but considering the context, the phrase has a more significant implication. Jesus and the disciples are "on the way"—indirect though it may be—to Jerusalem, both chronologically and theologically. As they grow nearer to the crucifixion, Jesus takes the time to teach them what they need to know.