What does it mean to be born again?

John 3:

3 Jesus answered and said to him, "Truly, truly, I say to you, except anyone be born from above, he is not able to see the kingdom of God."

i.e., born from above or born again

5 Jesus answered, “Very truly I tell you, no one can enter the kingdom of God unless they are born of water and the Spirit. 6 Flesh gives birth to flesh, but the Spirit gives birth to spirit. 7 You should not be surprised at my saying, ‘You must be born again.’ 8 The wind blows wherever it pleases. You hear its sound, but you cannot tell where it comes from or where it is going. So it is with everyone born of the Spirit.”

The Holy Spirit comes to you to cause you to be born again. It is a real supernatural event that happens in real-time.

John 14:

15 If you love Me, you will keep My commandments. 16 And I will ask the Father, and He will give you another Helper <Paraclete> to be with you forever—17 the Spirit of truth. The world cannot accept him, because it neither sees him nor knows him. But you know him, for he lives with you and will be in you.

If one is born again, he has the Paraclete Spirit dwells in his spirit/conscience forever.

23Jesus answered him, “If anyone loves me, he will keep my word, and my Father will love him, and we will come to him and make our home with him.

The Paraclete represents the Father, Son, and Holy Spirit.

The Holy Spirit is connected to our human spirit, Romans 8:

16 The Spirit himself bears witness with our spirit that we are children of God,

This is the 100% guarantee for eternal life, John 10:

28 I give them eternal life, and they shall never perish; no one will snatch them out of my hand.

The Paraclete is a special operation of the Holy Spirit. He is the Indwelling Spirit. He enables us to hear God. I can sense him in my spirit anytime all the time.