A while ago I set myself the task of explaining the gospel in a hundred words. I came across the brief explanation of the gospel by John Stott (it is more than a hundred words).
"The good news, then is this: that Almighty God loves us in spite of our rebellion against him; that he came after us himself is the person of his Son Jesus Christ; that he took our nature and became a human being; that he lived a perfect life of love, having no sins of his own for which atonement needed to be made, but that on the cross he identified himself with our sin and guilt. In two dramatic New Testament expressions he was 'made ... to be sins for us' and became 'a curse for us' (2 Corinthians 5:21; Galatians 3:13). For in those awful three hours of God-forsaken darkness he endured the condemnation our sins deserved. But now, on the ground of Christ's sin-bearing death, God offers us a full and free forgiveness, together with a new birth and a new beginning in the power of the resurrection."