In A nutshell the Gospel is the basis of Christianity. Most of us are familiar with the story of Adam and Eve. God made Man, then made Woman. Serpent deceives Woman into eating forbidden fruit, Man eats fruit and sin enters the world. Here is the sad part. God is perfect, therefore he cannot live with imperfection. Sin. So from that point on God and Man were separated. But God still Loves Man (us) with all his heart, so he knew something had to be done.
In order to bridge this gap between God and man he sends Jesus. The son of God, who is an extension of his very self (God), to earth. Jesus was to live a perfect life, free of blame and then suffer the consequence of sin that he never committed! And that is exactly what he did. Jesus lived on earth for 33 years and didn't sin once! Then he was persecuted, tortured and Crucified. In death Jesus became the perfect sacrifice. The blameless "Lamb of God"!
Then, within three days he stormed the gates and fought for the key to hell! Gaining dominion over death which is the price of sin. On the third day he Rose with the power over sin in hand so that now we may have eternal life through him.