At a time when the Romans ruled the Jews, news began to stir of a Jewish man who claimed authority. In John chapter one we see John the Baptist give way to the ministry of Jesus. In Chapter two we read of Jesus' first recorded miracle when He demonstrated authority over the elements, turning the water into wine. Later in that chapter we see Jesus' authority in the temple when He overturned the tables and drove out the merchants and the money changers. When the Jews inquired as to the authority Jesus had to do these things, He answered with John 2:19, "Destroy this temple, and in three days I will raise it up." This response left the Jews with even more questions, but it is only recorded that one person decided to go to the source for answers.
Jesus did not alter the message to make it more palatable.
In John chapter 3 we meet Nicodemus, a ruler of the Jews and a Pharisee. The Pharisees rooted their faith in tradition and seemed to have lost sight of (and desire for) the Messiah. However, Nicodemus had questions, so he came to Jesus by night. He opened by recognizing Jesus as being a teacher sent from God. Jesus skipped the pleasantries and went to the heart of the matter. He said, "Verily, verily, I say unto thee, Except a man be born again, he cannot see the kingdom of God." Though this terminology was foreign to Nicodemus, Jesus did not alter the message to make it more palatable. Jesus went on to explain, "That which is born of the flesh is flesh; and that which is born of the Spirit is spirit." Nicodemus still was not getting it. Then in verses 14 and 15, Jesus used terminology that a scholar of the Old Testament was sure to understand. "And as Moses lifted up the serpent in the wilderness, even so must the Son of man be lifted up: That whosoever believeth in him should not perish, but have eternal life." At this point Jesus has informed Nicodemus of a spiritual birth and the fact that the way to eternal life is through faith in the Son of man who must be lifted up. In John 3:16, Jesus gave Nicodemus the why, the what, the who and the how, all in one verse.
For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life.
Jesus is the Son of God. He was the only payment acceptable and pleasing to God the Father. Because Jesus was lifted up, all who look to Him in faith, believing that God hath also raised Him from the dead, shall be saved.