The Catechism in Questions & Answers

114. What does the majestic title “Son of Man” mean?

When the term “Son of Man” is used as a majestic title, it is not referring to the son of a man, but rather a heavenly being that judges and rules over mankind.
At the time of Jesus, devout Jews were expecting the “Son of Man” who would assume rule over the world from God. According to John 3: 13, Jesus also identifies Himself as the Son of Man who came down from heaven. As such He has power to forgive sins and save (cf. Matthew 9: 6).

“For the Son of Man has come to seek and to save that which was lost.” Luke 19: 10