John was sent to tell people about “the light” (vv. 7–8). The light is Jesus Christ. John’s job was to tell the world of the coming of the Messiah, Jesus.
John was doing amazing things, things that caused people to think he was the Messiah (v. 20–25). There were also prophecies that Elijah would return prior to the return of the Lord (Mal 4:5). John’s appearance even reminded some of Elijah (v. 21; 2 Kings 1:8).
The beginning of Jesus’ earthly ministry was announced by John the Baptist. It was not a secret. The second advent of Jesus, his triumphal return, will occur. As his return gets close, there will be signs of his coming. We should rejoice in the expectation of seeing them.