Cornelius was a Roman centurion stationed in Caesarea, and apparently the first Gentile to convert to Christianity (Acts 10:1-49). He was sympathetic to the Jews and believed in one God. He opposed pagan worship. God gave Cornelius and the apostle Peter both a heavenly vision.
The vision to Peter occurred three times and meant it was permissible to eat foods that the Judaism considered unclean. The vision also meant that no person could be considered unclean either; Gentiles, as well as Jews, could receive the teachings of Jesus. Peter, obeying the vision, traveled to Caesaerea to meet Cornelius.
While preaching to Cornelius "the Holy Spirit fell upon all who were listening to the Word" and they started "speaking in tongues and glorifying God." Peter baptized them in the name of the Lord. This incident marked the expansion of the early church to include Gentiles as well as Jews.
The church in Jerusalem was scandalized by Peter's association with the Gentiles, but he silenced their criticism by saying, "who was I that could withstand God? (Acts 11:17).