Jesus tries to explain spiritual things in an earthly way. Given it has been over 2000 years, it can be even harder for us to understand. But know, if we are not "born" of God than we do not have life.
3:1 Now there was a man of the Pharisees named Nicodemus, a ruler of the Jews. 2 This man came to Jesus by night and said to him, “Rabbi, we know that you are a teacher come from God, for no one can do these signs that you do unless God is with him.” 3 Jesus answered him, “Truly, truly, I say to you, unless one is born again he cannot see the kingdom of God.” 4 Nicodemus said to him, “How can a man be born when he is old? Can he enter a second time into his mother's womb and be born?” 5 Jesus answered, “Truly, truly, I say to you, unless one is born of water and the Spirit, he cannot enter the kingdom of God. 6 That which is born of the flesh is flesh, and that which is born of the Spirit is spirit. 7 Do not marvel that I said to you, ‘You must be born again.’ 8 The wind blows where it wishes, and you hear its sound, but you do not know where it comes from or where it goes. So it is with everyone who is born of the Spirit.”
9 Nicodemus said to him, “How can these things be?” 10 Jesus answered him, “Are you the teacher of Israel and yet you do not understand these things? 11 Truly, truly, I say to you, we speak of what we know, and bear witness to what we have seen, but you do not receive our testimony. 12 If I have told you earthly things and you do not believe, how can you believe if I tell you heavenly things? 13 No one has ascended into heaven except he who descended from heaven, the Son of Man. 14 And as Moses lifted up the serpent in the wilderness, so must the Son of Man be lifted up, 15 that whoever believes in him may have eternal life. (ESV)
25 I will sprinkle clean water on you, and you shall be clean from all your uncleannesses, and from all your idols I will cleanse you. 26 And I will give you a new heart, and a new spirit I will put within you. And I will remove the heart of stone from your flesh and give you a heart of flesh. 27 And I will put my Spirit within you, and cause you to walk in my statutes and be careful to obey my rules. (ESV)