Because God loves each of us, He sent His one and only Son, Jesus Christ from Heaven to be born as a man on the earth. Jesus lived a perfect life- the only one who has been perfect. And He chose to willingly die on the cross to take the penalty for our sins. No one else could do that because no one else is perfect. This is the heart of the gospel. "Gospel" means "good news".
"For God so loved the world that he gave his one and only Son, that whoever believes in him shall not perish but have eternal life. 17 For God did not send his Son into the world to condemn the world, but to save the world through him. 18 Whoever believes in him is not condemned, but whoever does not believe stands condemned already because they have not believed in the name of God’s one and only Son."
(John ch. 3 verses 16-18)