In Acts 8 when persecution started against Christians in Jerusalem, God used the scattering of Christians to spread the gospel to all parts of the ancient world. In the case of Philip, he went down to Samaria. You may remember Samaria and Samaritans from the parable of the "Good Samaritan" in Luke 10. But do you know how Jews saw Samaritans?
Samaritans are the descendants of Upper Kingdom of Israel (you may remember after King Solomon's reign that Israel split into two different nations). But because they were captured by the King of Assyria and intermarried with the peoples of that empire, they inherited some practices from the other pagan nations. They were returned to Israel at the same time as Ezra and Nehemiah, but never fully accepted the new Temple in Jerusalem. Sometime around 4 BC, they even built their own temple at Mount Gerizim (near Shechem). Shortly before the time of Jesus, in an attempt to avoid persecution from the Roman Empire, the Samaritans even had their temple declared "The Temple of Jupiter Hellenius" (i.e. the Roman head God, called Zeus by the Greeks). It had been bad enough to question the authority of the temple in Jerusalem, but dedicating the Samaritan temple to a pagan god was the last straw for the Jews. After this point, they considered Samaritans to be the lowest of the low and rejected any family connection with them.
That it why it is so shocking that Philip went to Samaria and preached the gospel. Before this, all preaching of the gospel in Acts had been to Jews. Now, the grace of God was being extended to a people who were decidedly non-Jewish, though they were not without any link to Abraham. And even the apostles recognized this, as they sent Peter and John down to minister to them. What can we expect next from the Church in Acts?