The term “born again” refers to the belief that in order for an individual to become a member of God’s Kingdom, they must experience a new birth. This is majorily a Protestant term built around the scripture John 3:3-6 where Jesus tells Nicodemus, a Pharisee, that in order to see the Kingdom of God, one must be born again.
Jesus was not describing a physical rebirth, which you will see in the scripture. Rather, a spiritual rebirthing, signifying a new life.
John 3:3-6 reads as follows:
Jesus replied, “Very truly I tell you, no one can see the kingdom of God unless they are born again.”
“How can someone be born when they are old?” Nicodemus asked. “Surely they cannot enter a second time into their mother’s womb to be born!”
Jesus answered, “Very truly I tell you, no one can enter the kingdom of God unless they are born of water and the Spirit. Flesh gives birth to flesh, but the Spirit gives birth to spirit.