What does it mean to be born again in Christian theology?

The term 'born again' is thoroughly explained in John 3:3-5, where Jesus tells Nicodemus that one must be born again to see the kingdom of God. This rebirth is a work of the Holy Spirit where an individual is regenerated, moving them from death to life and enabling them to respond to God in faith. Ephesians 2:1-5 elaborates on this by showing that we were dead in our trespasses and sins but made alive by God through His mercy. This regeneration is essential, as it signifies a complete transformation in a person's spiritual state—making it possible for them to believe and live according to God's will.