Final answer:
The Baptism by St. John the Baptist marked the beginning of Jesus' public ministry and symbolized his acceptance of his divine mission. It also testified to John's role as the forerunner of Christ and affirmed Jesus' identity as the Son of God.
Step-by-step explanation:
The significance of the Baptism by St. John the Baptist is that it marked the beginning of Jesus' public ministry. It symbolized Jesus' acceptance of his divine mission and his commitment to fulfill God's plan for salvation. The Baptism also served as a testimony to John's role as the forerunner of Christ, as he recognized Jesus as the long-awaited Messiah and affirmed his identity as the Son of God.