Now I would remind you, brothers,of the gospel I preached to you, which you received, in which you stand, and by which you are being saved, if you hold fast to the word I preached to you— unless you believed in vain.
For I delivered to you as of first importance what I also received: that Christ died for our sins in accordance with the Scriptures, that he was buried, that he was raised on the third day in accordance with the Scriptures, and that he appeared to Cephas, then to the twelve. Then he appeared to more than five hundred brothers at one time, most of whom are still alive, though some have fallen asleep. Then he appeared to James, then to all the apostles.
(1 Cor 15:1 - 7)
The one and only God - Creator of heaven and earth, who is holy, righteous and loving - made man in His image to know Him.
But man sinned and cut ourselves off from Him. Because man is fallen and sinful our relationship with God, with each other and with creation is broken.
In His great love, God became man in Jesus, lived a perfect life, and died on the cross, thus fulfilling the law himself and taking on himself the punishment for our sins of all those who would ever turn and trust in Him. He rose again from the dead,showing that God had accepted Christ's sacrifice and that God's wrath against us had been exhausted.
He now calls us to repent of our sins and to trust in Christ alone for our forgiveness. If we repent of our sins and trust in Christ, we are born again into a new life, an eternal life with God.