John the Baptist wasn't his real name. We call him that because Scripture calls him that. This title was given him because he baptized people in water when they wanted to repent of their sins. John's baptism was a baptism of turning away from sin and turning back to God.
Then Jesus went from Galilee to the Jordan River to be baptized by John. But John tried to talk Him out of it. "I am the one who needs to be baptized by You," he said, "so why are You coming to me?" But Jesus said, "It should be done, for we must carry out all that God requires. " So John agreed to baptize Him. After His baptism, as Jesus came up out of the water, the heavens were opened and He saw the Spirit of God descending like a dove and settling on Him. And a voice from heaven said, "This is My dearly loved Son, who brings Me great joy." (Matthew 3:13-17 NLT)
While Apollos was at Corinth, Paul took the road through the interior and arrived at Ephesus. There he found some disciples and asked them, "Did you receive the Holy Spirit when you believed?" They answered, "No, we have not even heard that there is a Holy Spirit." So Paul asked, "Then what baptism did you receive?" "John's baptism," they replied. Paul said, "John's baptism was a baptism of repentance. He told the people to believe in the one coming after him, that is, in Jesus." On hearing this, they were baptized into the name of the Lord Jesus. When Paul placed his hands on them, the Holy Spirit came on them… (Acts 19:1-7 NIV)
After Jesus was baptized, his disciples started baptizing people who wanted to be followers of Jesus rather than John. This baptism would prove to be more than a baptism of repentance. More was being added to the meaning. Now they were being baptized to repent and become a Jesus-follower. Later, after Jesus died for us, rose again, ascended into heaven and sent His Spirit back for us; the meaning changed again. When asked what it was about, Peter replied, "Repent and be baptized...for the forgiveness of your sins. And you will receive the gift of the Holy Spirit..." (Acts 2:38-39) Now baptism had even more meaning. It was about repentance (like John's), becoming a Christ-follower (like Jesus' disciples), receiving forgiveness for sins (now that Jesus had died to take them away - the gift is offered to us), and receiving the gift of the Holy Spirit (which Jesus sent back to help us). The meaning of baptism grew more and more rich as the pages of Scripture unfolded. Now, it has all of this richness of meaning for us today!