Just before Jesus began his public ministry, he travels from Galilee to the Jordan River, where he is baptized by John the Baptist.
John was the forerunner to Jesus, preparing the people of Israel for the public ministry of Jesus. He is the one who announced that Jesus is the Messiah who is sent by God to take away the sin of the world.
During the baptism, the Holy Spirit descends from above and rests on Jesus, anointing him as the Messiah.
The baptism of Jesus, as described in the Gospel of Matthew:
15 But Jesus, answering, said to him, “Allow it now, for this is the fitting way for us to fulfill all righteousness.” Then he allowed him.
16 Jesus, when he was baptized, went up directly from the water: and behold, the heavens were opened to him. He saw the Spirit of God descending as a dove, and coming on him. 17 Behold, a voice out of the heavens said, “This is my beloved Son, with whom I am well pleased.” (Matthew 3:13-17, WEB)
Read more in the book Jesus the Miracle Worker: The 46 miracles of Jesus explained in chronological order (The Jesus Books) -- now available at amazon.